OBJECTIVE: To assess the risk of breast, ovarian and prostate cancer in the families of men with prostate cancer. PATIENTS AND METHODS: A case-control study was performed by interviewing patients with prostate cancer and obtaining detailed information on family histories of cancer. Controls were hospital-based patients, of a similar age to the cases, with bladder cancer or benign prostatic hypertrophy. RESULTS: A total of 209 cases and 322 controls were interviewed; of the cases, 22.5% had family members with a history of one or more of breast, ovarian or prostate cancers, compared with 15.2% of controls (P < 0.05). The odds ratio (OR) of having prostate cancer when there was a positive family history was 8.22 and the OR of a female relative of a patient with prostate cancer having breast cancer was 1.51. There was no apparent increased risk of ovarian or any other cancer. CONCLUSIONS: We confirm previous reports of an increased incidence of prostate cancer in the families of men with prostate cancer and report a similarly increased incidence of breast cancer in female relatives. We suggest that detailed family histories be taken routinely and intend to analyse blood samples provided from this study for genetic abnormalities.