In jazz improvisation, the meter of the original theme is strictly preserved, and the middleground harmonies are maintained, while the original melody is varied freely, especially with respect to its grouping structure—where phrases begin and end. This poses problems for theories of phrase rhythm that rely on a tonal definition of the phrase. In this paper, I propose a new approach to jazz phrase rhythm. First, I divide a melody into segments on the basis of four criteria. Then I classify each segment on the basis of its relationship to the meter and to surrounding segments. The result is a hierarchy of metrically defined phrases. Phrase rhythm consonance and dissonance are the alignment or misalignment of phrases with the meter. Skilled soloists manipulate phrase rhythm as they would any other element of a solo. I conclude with an ambiguous example, to demonstrate how phrase-rhythm analysis can present competing interpretations of the same passage.