OBJECTIVE: To study the lifetime occurrence of prostatitis in Finnish men and their exposure to the disease. Subjects and methods A population-based cross-sectional survey was conducted in the two most northerly provinces of Finland (Oulu and Lapland). Altogether, 2500 male residents aged 20-59 years were chosen at random to complete a questionnaire on prostatitis. The data were collected between June 1996 and October 1997. Replies were received from 1832 men, giving a response rate of 75%. RESULTS: The overall lifetime prevalence of prostatitis was 14.2%. The risk of having or having had prostatitis increased with age, being 1.7 times greater in men aged 40-49 years than in those aged 20-39 years, and 3.1 times greater in those aged 50-59 years. The overall incidence was 37.8/10 000 person years. More than a quarter of the 261 men who had or had had prostatitis symptoms (27%) suffered from them at least once a year, while 16% suffered from persistent symptoms; 63% of the men with prostatitis had their worst symptoms during the winter (November-March). Neither education nor profession had much influence on the occurrence of prostatitis, but divorced and single men had a lower risk than married men. Most patients felt they had not received enough information about the disease at their first visit to a general practitioner. CONCLUSIONS: The results of this survey showed that the occurrence of prostatitis symptoms in men living in northern Finland is higher than that reported in other parts of the world. This could be partly caused by the cold climate.