The optimal management of chronic abacterial prostatitis is not known. A systematic review of the literature was done to answer the following questions: Are there accurate, reliable tests to diagnose chronic abacterial prostatitis? Are there effective therapies for it? Studies were identified by searching MEDLINE (1966 to 1999), the Cochrane Library, and bibliographies of identified articles and reviews and by contacting an expert Diagnostic test articles were included if they reported on controlled studies; treatment articles were included if they reported on randomized or controlled trials. No language restrictions were applied. For each selected article, two investigators independently extracted key data on study design, patient characteristics, diagnostic test or treatment characteristics, and outcomes. 19 diagnostic test articles and 14 treatment trials met the inclusion criteria The disparity among studies in design, interventions, and other factors precluded quantitative analysis or pooling of the findings. Diagnostic test articles included 1384 men (mean age, 33 to 67 years) and evaluated infection; inflammation, immunology, and biochemistry; psychological factors; and ultrasonography. Treatment trials included 570 men (mean age, 38 to 45 years) and evaluated medications used to treat benign prostatic hyperplasia, anti-inflammatory drugs, antibiotics, thermotherapy, and miscellaneous medications. No trial was done in the United States. There is no gold-standard diagnostic test for chronic abacterial prostatitis, and the methodologic quality of available studies of diagnostic tests is low. The few treatment trials are methodologically weak and involved small samples. The routine use of antibiotics and alpha-blockers to treat chronic abacterial prostatitis is not supported by the existing evidence.