English aspectual verbs have been analyzed as ambiguous between control and raising predicates, based on evidence that their subjects can be either thematic or non-thematic (Perlmutter 1968, 1970; Ross 1972). However, a closer examination of the relevant data shows that the only valid argument for the control analysis is the fact that aspectual verbs are compatible with the imperative. Analyzing aspectual verbs as pure raising verbs is also problematic, since such an analysis cannot account for the imperative facts or the fact that sentences with aspectual verbs are mono-clausal. Furthermore, the control/raising analysis does not account for the distribution of two types of clausal complements of aspectual verbs: gerundive and infinitive. As an alternative, this paper presents a functional head analysis of aspectual verbs, according to which they are heads of an Aspect Phrase (Travis 1991), projecting in two positions: above vP (High-Aspect) and below vP (Low-Aspect). The complements of High-Aspect and Low-Aspect are realized as infinitives and gerundives, respectively. Both language-specific and cross-linguistic arguments for the analysis are presented based on adverb interpretation, quantifier scope, and passive facts. An analysis of the imperative facts based on the proposed analysis is also presented and shown to make the right prediction.