A lack of consensus has existed regarding the interaction of English modals with categories such as tense, and individual modal forms can vary in the extent to which they make assertions regarding temporal reference. The present work attempts to provide a compositional semantic account of English modals by proposing that these forms may be inflected both for tense and for mood. The cross-linguistic status of inflectional moods such as the subjunctive is examined; it is argued that an inflectional subjunctive exists in Modern English with semantic properties similar to those of comparable forms in older Indo-European languages, and the extent to which linguistic cues would permit learners of English to acquire such a category is discussed. Data on English modals are reviewed in light of the analysis proposed here to determine its compatibility with observed usage. It is suggested that the analysis proposed here has certain advantages over models in which the observed semantic range of English modals is presented in terms of an unprincipled heterogeneity.