This report summarizes the initial phase of research with neurological patients on timing functions. Parkinsonian, cerebellar, cortical and peripheral neuropathy patients as well as college aged and elderly control subjects were tested on two separate measures of timing functions. The first task involved the production of timed intervals and used the repetitive tapping task developed by Wing and Kristofferson. The second task measured the subjects' perceptual ability to discriminate comparable temporal intervals. The tapping results indicate that cortical, cerebellar, and peripheral neuropathy patients are more variable in implementing their responses. In addition, the cortical and cerebellar patients demonstrate increased variability in an internal timekeeping process. A small number of basal ganglia patients also showed a deficit in the timing process. These results are accounted for by postulating that the timing of interval can only commence once the central command for the preceding response has been issued. Thus, deficits in any central neural system can affect the integrity of the timing process. Nonetheless, the cerebellum appears to play a primary role in timing functions, since the cerebellar patients were the only group who showed a deficit in the perception of time task. (Author/JAZ)