The pathogenesis, clinical signs and symptoms, diagnosis and treatment of chronic bacterial prostatitis (CBP) are reviewed. The most common organism associated with CBP is Escherichia coli, although infections with Klebsiella, Enterobacter, Proteus, Pseudomonas, and enterococci have also been documented. The only symptoms of CBP may be those of an acute urinary-tract infection. The use of simultaneous quantitative urine cultures represents the most accurate method for diagnosing CBP. The use of trimethoprim-sulfamethoxazole, the current drug of choice for CBP, is based on results in animals showing good penetration of trimethoprim into acidic prostatic fluid and the knowledge that normal human prostatic fluid is acidic. Studies in patients with CBP, who have alkaline prostatic fluid, have demonstrated poor penetration of trimethoprim into prostatic fluid, which may explain the cure rate of about 40% seen with trimethoprim-sulfamethoxazole. A few patients have been treated successfully with kanamycin and streptomycin, but these drugs must be given by injection. Carbenicillin indanyl sodium has been associated with cure rates of almost 70% in a small number of studies. Both doxycycline and minocycline have been used to treat CBP, but inadequate urine-culture data make these studies difficult to evaluate. Erythromycin produced a cure rate of 88% in one study in patients who received 500 mg (as the stearate salt) four times daily for 14 days. Local injection of antibiotics into the prostate has been reported to be effective in a few cases. Although controlled comparative trials with trimethoprim-sulfamethoxazole are needed, carbenicillin indanyl sodium and erythromycin appear to be the drugs of choice for treating CBP; trimethoprim-sulfamethoxazole should be reserved for patients with CBP unable to tolerate or unresponsive to therapy with these agents.