Between January 1, 1935 and December 31, 1980, adult polycystic kidney disease (APKD) was diagnosed in 40 residents of Olmsted County, Minnesota, resulting in an age- and sex-adjusted annual incidence rate of 1.38/100,000 person-years. In addition, 16 cases were detected at autopsy, increasing the rate to 2.06. It is estimated that 16 additional cases would have been discovered had all deaths come to autopsy, resulting in a rate of 2.75, or approximately twice the incidence rate of cases diagnosed during life. Because of improvements in medical care and diagnostic techniques, APKD has been diagnosed earlier and more frequently in the recent decades. This, along with therapeutic advances, explains the improvement in kidney and patient survival for the patients diagnosed during 1956-1980, as compared to those diagnosed during 1935-1955. Normotension at diagnosis tended to be associated with better kidney and/or patient survival. Cardiovascular disease was the leading cause of death.