This paper reviews the epidemiologic studies of benign prostatic hyperplasia in relation to prostate cancer. Such relation was investigated in epidemiologic studies but none have provided clear evidence suggesting an etiologic role for benign prostatic hyperplasia in the development of prostatic cancer. In this regard comprehensive understanding of benign prostatic hyperplasia in relation to prostate cancer would require examination of anatomic relation endocrine factors in the development and progression of benign prostatic hyperplasia stromal-epithelial interactions in the control of prostate growth biochemical and genetic alterations and their prostate-specific antigen (serine protease). In addition study on prostate size urinary symptoms and propensity for prostate cancer detection are also needed. Biological evidence suggests that benign prostatic hyperplasia and prostatic carcinoma share common predisposing factors. Since both share a number of determinants a problem on the epidemiologic study of prostate cancer is whether to consider benign prostatic hyperplasia as a potential confounder. Moreover detection bias may arise in such epidemiologic study.