The objective of the present study was to record the use of antiparkinsonian drugs (APD) in Denmark and discuss estimates of the incidence and prevalence rates of Parkinson's disease (PD). The main indication for treatment with APD is idiopathic PD. The use of APD is, therefore, an indicator of the epidemiology of PD and Parkinsonism. We used a drug tracer design, which previously has been found applicable in estimating the frequency of PD. From a national prescription database, all persons who purchased APD from 1995 to 2002 could be identified on an individual level. Results show an age-standardized prevalence rate for APD purchase of 164.0 persons per 100,000, and an incidence rate of 55.9 persons per 100,000. The total number of persons purchasing APD was 11,656 per year on average. Our results showed higher figures of persons purchasing APD than the estimated prevalence of idiopathic PD in Denmark, which is approximately 100 persons per 100,000, corresponding to 5,000 to 6,000 persons. The differences might in part be explained by other indications for APD prescription in addition to PD and in part by misdiagnosis. However, the possibility of somewhat higher incidence and prevalence rates of PD than hitherto estimated should be considered.