One hypothesis about the temporal control system of speech postulates two levels of control, a motor planning level and a motor execution level [J.‐F. Bonnot, J. d'Acoust. 2, 287–296 (1989)]. This study of four ataxic dysarthric and four unimpaired speakers was designed to explore the role of cerebellar function in speech and identify some of the linguistically and physiologically determined aspects of speech timing. Preliminary results reveal a systematic but nonuniform timing disruption: a tendency for compensatory shortening effects to be preserved, even in the presence of segmental lengthening by the dysarthric speakers, and an absence of terminal lengthening effects. These results suggest that compensatory shortening is planned and sufficiently robust to survive the temporal disruption at the motor execution level, but that terminal lengthening arises from the execution of a motor sequence, rather than being part of the motor plan. [Work supported by Ministere de Recherche et Technologie, France, St. John's Univ. William Paterson College, and NIH Grants DD‐00121 and RR‐05596 to Haskins Labs.]