PURPOSE: Various medical conditions, infectious agents, sexual, and hormonal factors have been investigated in relation to prostate cancer risk. Given inconsistent results these factors were examined in this study.METHODS: This population-based case-control study was conducted in northeastern Ontario from 1995 to 1999. Cases (n = 760), aged 45 to 84 at the time of diagnosis, were identified through the Ontario Cancer Registry and diagnosed between January 1995 and December 1998. Controls (n = 1,634) were age-frequency matched and were selected from the northeastern Ontario population using published telephone listings. Mail and telephone questionnaires were used for data collection. Logistic regression was used to investigate risk associated with: 1) particular medical conditions and 2) hormonal and sexual factors. Cases were subdivided into those with symptoms of prostate disease and those with few or no such symptoms.RESULTS: Symptomatic cases who reported a history of venereal disease (age-adjusted odds ratio (OR) = 2.11, 95% confidence interval (CI) 1.18-3.80) and vasectomy (age-adjusted OR = 1.49, 95% CI 1.14-1.95) were at significantly increased risk of prostate cancer. Asymptomatic cases who reported a check-up at least once a year were at increased risk (age-adjusted OR = 1.46, 95% CI 1.08-1.98). Asymptomatic and symptomatic cases who reported a history of prostate cancer in a first degree relative were at increased risk (age-adjusted OR = 2.41, 95% CI 1.64-3.54; age-adjusted OR = 3.18, 95% CI 2.28-4.45, respectively). Symptomatic cases with a history of urinary tract infection were at non-significantly increased risk (age-adjusted OR = 1.31, 95% CI 0.98-1.76). Heart disease, mumps, allergies, and height were generally not associated with prostate cancer.CONCLUSIONS: A history of venereal disease, family history of prostate cancer, and vasectomy were positively associated with prostate cancer. Further investigation of selected medical conditions, sexual, and hormonal factors in prostate cancer development is warranted.