Sentences may pertain to states or processes or events. They may express boundedness, duration, repetition, frequency, and many other forms of temporality. How do they do this? Henk Verkuyl presents here a theory about aspectual properties of sentences in natural languages. A Theory of Aspectuality brings together the fruit of his thinking on the subject over the past 20 years, and will interest all those working on aspect and the semantics of noun phrases. It promises to be a major contribution to our understanding of the subject.