This paper reports the results of an inquiry into the question of category versus continuum in intonation. Variants of the English rise-fall-rise pattern were used to study whether tonal alignment is a categorical or gradient distinction. LPC resynthesis was used to construct a set of stimuli in which the alignment of the F0 rise-fall varied in small steps. Subjects heard the stimuli in randomized order and imitated what they heard. The position of the F0 peak relative to the onset of the stressed vowel was measured in each response. Systematic deviations between the peak placement in the stimuli and those in the responses revealed the existence of two categories. We conclude that tonal alignment functions as a binary distinction in English intonation.