A prevalence survey on Parkinson's disease (PD) was performed in the Republic of San Marino, which is the smallest independent state in the world, and is located near the Adriatic coast, within Italy. On April 30, 1986, it had a population of 22,322. We found 34 cases of PD (17 men, 17 women). Crude prevalence ratio per 100,000 population was 152 (154 for men, 150 for women) with an age-adjusted ratio of 185 (both sexes). This study shows that the prevalence of PD in the Mediterranean area of South Europe is similar to that in North Europe and the United States.