Benign diseases of the prostate are common in the general male population, and prostate cancer is the most common cancer in men. Uncertainty as to the nature of the association between benign and malignant disease is a source of concern for patients and clinicians.To determine the likelihood of men with benign prostate disease developing prostate cancer compared with men without disease.Incident matched case-control study.All incident cases of prostate cancer (n = 984) were identified in a nationally representative community-based population, and each was matched by age with two controls with no prostate cancer (n = 1968). Participants' records of the previous 5 years were searched for diagnoses of benign prostate disease. Analyses investigated an a priori hypothesis that clinicians may record disease as benign until proven to be malignant, causing misleading significant associations between benign and malignant diagnoses.There was a significant association between a diagnosis of prostate cancer and a benign diagnosis at any time in the previous 5 years: odds ratio (OR) 1.57 (95% confidence interval [CI] = 1.32 to 1.88). However, there was no significant association when benign diagnoses within 6 months and within 12 months of cancer diagnoses were excluded: OR 1.19 (95% CI = 0.97 to 1.46) and OR 1.00 (95% CI = 0.79 to 1.27) respectively.Findings from this study suggest that unless prostate cancer is detected within 6 months, men diagnosed for the first time with benign disease are at no greater risk of prostate cancer than those with no recorded prostate disease.