Article 83 of the European Patent Convention simply requires that an application disclose the invention in a manner sufficiently clear and complete to be carried out by one skilled in the art. Article 84 requires that the claims be clear and concise, and supported by the description. The Implementing Regulations flesh out these requirements to some extent by requiring that the description shall inter alia:

Apart from these general provisions, certain specific requirements were set out in the rules for inventions relating to microorganisms.

If the initial approach of the EPO to questions of obviousness was Germanic, the approach to sufficiency was distinctly British. [68] From the beginning, it has been clear that claims may be drafted broadly and do not have to be limited to specifically described embodiments or examples. As originally published, the Guidelines recognized that:

...claims are generalizations from one or more particular examples. The extent of generalization permissible is a matter which the examiner must judge in each particular case in the light of the relevant prior art. Thus, an invention which opens up a whole new field is entitled to more generality in the claims than one which is concerned with advances in a known technology. A fair statement of claim is one which is not so broad that it goes beyond the invention nor yet so narrow as to deprive the applicant of a just reward for the disclosure of his invention. The applicant should be allowed to cover all obvious modifications, equivalents to and uses of that which he has described. In particular, if it is reasonable to predict that all the variants covered by the claims have the properties or uses the applicant ascribes to them in the description he should be allowed to draw his claims accordingly...

A claim in generic form, i.e., relating to a whole class e.g. of materials or machines, may be acceptable even if of broad scope, if there is fair support in the description, and there is no reason to suppose that the invention cannot be worked through the whole of the field claimed. Where the information given appears insufficient to enable the skilled man to extend the teaching of the description to parts of the field claimed, but not explicitly described, by using routine methods of experimentation or analysis, the examiner shall require the applicant to satisfy him that the invention can in fact be readily applied, on the basis of the information given, over the whole field claimed or, failing this, to restrict the claim to accord with the description.

Apart from modifications to deal with speculative claiming (which the Guidelines now say should be objected to as being based on insufficient disclosure unless the effects of what is claimed can readily be predetermined or assessed,) the wording of the original Guidelines remains intact. It still remains to be seen how courts in countries that have traditionally dealt with claims of much narrower scope (such as Germany and Sweden) will deal with broad claims of the type granted by the EPO.

It should be noted that while the EPO is able to reject applications on the ground that they do not comply with the requirements of Article 84 that the claims are supported by the disclosure, failure to comply with the requirements of this provision is not a ground of opposition to a European patent, although it may be possible to argue the issue under the guise of insufficiency of disclosure. [69]

6.1 Enabling Disclosure

The core issue of enabling disclosure had until recently been addressed on only a few occasions. In Genentech I[70] the Appeal Board indicated that the essential requirement is that at least one way of carrying out the invention is disclosed such that one skilled in the art can carry it out. This principle was, however, discussed further in Fuel oils/Exxon [71] where a distinction was drawn between cases where one method was described that was of general applicability throughout the range of what was claimed and other situations where, for example, chemical compounds claimed in an application could not all be produced by the described method or by the application of common general knowledge. [72]

In the Exxon case itself, a claim to a fuel oil containing small wax crystals was held to lack support in the description because this had taught that certain additives were necessary to achieve the stated size range and the claim made no reference to such additives. Claims need to be commensurate with the technical consideration described in the specification if they are to be regarded as properly supported. [73] Thus if, as in the Exxon case, the specification states that certain features are essential to produced the promised result, a claim that lacks those features is not supported by the specification. [74]

The mere fact that some functionally defined starting materials may not be suitable does not in itself render the specification insufficient. [75] However, the amount of description and the number of examples needed may vary depending on the circumstances and the scope of claim. Thus in Modifying plant cells/Mycogen[76] it was said:

In certain cases a description of one way of performing the claimed invention may be sufficient to support broad claims with functionally defined features, foe example where the disclosure of a new technique constitutes the essence of the invention and the description of one way of carrying it out enables the skilled person to obtain without undue burden the same effect of the invention in the broad area by use of suitable variants of the component features. In other cases, more than one example may be necessary in order to support claims of a broad scope, for example where the achievement of a given technical effect by known techniques in different areas of application constitutes the essence of the invention and serious doubts exist as to whether the said effect can be readily obtained over the whole claimed range.

The board noted that the same degree of skill was required of skilled person who determined whether something was obvious or not and he/she who determined whether the description was sufficient. The only difference was that in determining sufficiency, knowledge of the invention could be added to the prior art. In the present case part of the appellant's case on obviousness had been that major research had been needed to see whether vector construction of the type of vector broadly defined in the claim in suit would work. The claim in question specified the vector as "comprising a plant promoter and a plant structural gene." In view of this, the Board concluded that the specification really only supported use of a vector "comprising a phaseolin promoter and a phaseolin structural gene" because this were all that the actual technical contribution to the state of the art justified.

In Redox Catalyst/Air Products [77] the Appeal Board excused an error in the specification on the ground that it was immaterial to the sufficiency of the disclosure if the skilled man could recognize what was required using his common general knowledge. It was, however, pointed out that "no undue effort was [to be] expected from the skilled man either in the way of ... [a] search or experimentation, let alone any necessity to exercise his inventive skill."

6.2 Cross References

In Amendment of Claims/Mobil, [78] the issue was whether a claim can be properly supported by a reference made to another document specifically cited in the specification as filed. The applicants sought to amend their claim to limit to certain features of a catalyst described in such a document. The Board held that while it is permissible to amend a claim to incorporate features of such a document, if this is done it is necessary to restrict the claims in accordance with the full disclosure of the cross-referenced document, and not select only certain features of its disclosure.

Thus, the Board refused to allow a claim to be amended to specify a particular type of "return member" when this had been described in another document referred to in the European application as filed in the following terms: "For further details of suitable locating, source and return members, reference should be made to..."

6.3 Clarity of Claiming

As noted above Article 84 of the Convention requires claims to be clear. Article 69 (discussed below in the context of infringement) permits one to refer to the specification to interpret a claim, unless the claim is so clearly bad (for example by containing mutually contradictory requirements) that "interpretation" was inappropriate. In Water-soluble cellulose ether/Aqualon [79] it was pointed out that whereas if one were referring to absolute values in a claim then if it was not obvious the test used to determine those values might have to be defined, no such requirement should exist for relative terms such as "water soluble". On the other hand relative terms themselves may be found to lack clarity. Thus in Lower alkyl/Nihon Nohyako[80] it was held that the term "lower alkyl" used to define certain substituents of a pyrazole derivative which was being claimed per se was lacking in clarity in the absence of any definition of the term in the specification. Having looked at text book uses of the term, the board felt that it had different meanings depending upon the context in which it was used and that there was not a sufficient reference point to define that context in the present case.