Some investigators reported pharmacogenetic differences in the metabolism of sulfur-containing drugs and lower plasma sulfate levels in patients with Parkinson's disease (PD) compared with controls. However, other group did not confirm these findings. We studied the plasma levels of sulfate by indirect atomic absorption spectrophotometry in 55 PD patients and 57 age and sex-matched controls. The plasma sulfate levels did not differ significantly between PD patients and control groups (mean +/- SEM 73 +/- 8 and 75 +/- 7 mg/l, respectively). They were not influenced by antiparkinsonian drugs and they did not correlate with age at onset, duration, Hoehn & Yahr staging or activities of daily living subscale of the Unified Parkinson's disease rating scale. There was a low but significant correlation of plasma sulfate levels with motor examination (r = -0.39, p < 0.05) and total score (r = -0.33, p < 0.05) of this scale in the PD group. These data suggest that plasma sulfate levels are apparently unrelated with the risk for PD.