We studied respiratory chain enzyme activities in spermatozoa homogenates from 12 untreated Parkinson's disease (PD) male patients and from 23 age matched healthy male controls. When compared with controls, PD patients showed significantly lower specific activities for complexes I+ III, II+III, and IV. However, citrate synthase corrected activities were similar in patients and controls. Values for enzyme activities in the PD group did not correlate with age at onset, duration, scores of the Unified Parkinson's Disease Rating Scales and Hoehn and Yahr staging. These results suggest that this tissue cannot be used to develop a diagnostic test for PD.