There is a set of French verbs which admits both indicative and subjunctive sentential complements. The indicative complement is correlated with a positive assertion about the truth of the complement; the subjunctive implies a neutral attitude or a non-assertion. When various sentential complement constructions are considered both in the indicative and the subjunctive moods, it can be shown in comparative examples that the assertions of these complements cannot be accounted for in terms of surface interpretation rules that do not affect the syntactic form of the complex. Instead, these complements form a class of assertions which must be marked in the underlying structure of the sentences that they affect. This must be so because the choice of complement is not dependent on the matrix verb but on semantic factors (e.g., assertion/non-assertion) of the complement clause itself, which are independent of the matrix. A particular interpretation is often implicit in a given sentential complement, and hence, in such cases, will determine the mood of that complement. Thus, the inclusion of assertion/non-assertion in underlying structure is well motivated and the underlying semantic structure affects the applicability of certain transformations. (Author/MHP)