The aim of the present study was to examine the occurrence of possibly associated diseases in 149 women with polycystic ovary syndrome (PCOS) 15-25 years after ovarian wedge resection. Diabetes mellitus was the only associated disease which showed a significantly increased occurrence. No significant change in cancers specific for the female gender was seen. Likewise, the relative risk of cardiovascular disease was not affected. However, the power of the statistical test was low. This long-term study indicates increased risk of diabetes mellitus in PCOS patients. The study group is too small to give any conclusions about other possibly associated diseases. Family histories, however, revealed that associated diseases are related to genetic disposition rather than to PCOS per se.