ABSTRACTS This research focuses on the interaction between modality and temporal elements in the interpretation of English discourses, investigating what restrictions should be put on the modeling of these elements in a formal semantic theory. The initial observations involve two kinds of phenomena. The first is modal subordination; it appears that in order to capture the mood- Reference Time interaction in discourses involving this phenomenon, we must treat instants and intervals in a model as non-primitive, defined in terms of events (themselves conceived as partial possible worlds). The second is the semantics of utterances which involve reference to times as well as modality, including conditionals and counterfactual conditionals. Such examples suggest further restrictions on the modeling of temporal phenomena, including new insights into the cross-world status of the notion of present, reflected in the notion of Speech Time, which is central to the interpretation of tense in a Reichenbachian approach, and in the lexical semantics of now and other temporal indexicals. The main goal of the research is to consider how to articulate the various restrictions with other considerations in the semantics of modal and temporal elements in English. The research bears as well on several open questions regarding the semantics of events and aspectual classes, the use of partiality in semantic modeling, and the role of context in interpretation.