Forty men with clinical prostatitis were studied to determine the value of symptomatology and categorization and 30 (75%) were classified as having prostatitis on the basis of prostatic localization studies. Of these 3 (10%) had chronic bacterial prostatitis, 18 (60%) had chronic abacterial prostatitis, and 9 (30%) had prostatodynia. No patient had acute bacterial prostatitis. Although Enterobacteriaciae were isolated from the 3 men with chronic bacterial prostatitis, these bacteria along with Staphlococcus aureus, Streptococcus faecalis, and Chlamydia trachomatis were isolated from a further 6 patients. The mean pH of the expressed prostatic secretion was measured for each group and was found to be 7.6 for those with chronic bacterial prostatitis, 7.1 for chronic abacterial prostatitis, 6.5 for prostatodynia, and 6.9 for those with urethritis suggesting that this test may be of value in the diagnosis of chronic bacterial prostatitis.