To elucidate the possible role of vitamin C in the risk for developing Parkinson's disease (PD), we compared serum levels of ascorbic acid (vitamin C), measured by a fluorometric method, of 63 PD patients using their spouses as the control group. The serum levels of vitamin C did not differ significantly between the groups (47.13 +/- 0.89 micrograms/ml for PD and 47.60 +/- 0.60 micrograms/ml for controls). There was no influence of antiparkinsonian therapy on vitamin C. Serum levels of vitamin C did not correlate with age, age at onset and duration of the disease, scores of the Unified PD Rating Scale or the Hoehn and Yahr staging in the PD group. These results suggest that serum vitamin C concentrations are apparently unrelated to the risk of developing PD.