We review the diagnosis, categorization, and treatment of prostatitis/chronic pelvic pain syndrome based on the National Institutes of Health (NIH) classification. Prostatitis is an extremely common syndrome that afflicts 2%-10% of men. Formerly a purely clinical diagnosis, prostatitis is now classified within a complex series of syndromes (NIH category I-IV prostatitis) that vary widely in clinical presentation and response to treatment. Acute bacterial prostatitis (category I) and chronic bacterial prostatitis (category II) are characterized by uropathogenic infections of the prostate gland that respond well to antimicrobial treatment. In contrast, chronic prostatitis/chronic pelvic pain syndrome (category III), which accounts for 90%-95% of prostatitis cases, is of unknown etiology and is marked by a mixture of pain, urinary, and ejaculatory symptoms with no uniformly effective therapy. Asymptomatic inflammatory prostatitis (category IV) is an incidental finding of unknown clinical significance. This review describes the current status of prostatitis syndromes and explores the future prospects of new diagnostic tools and therapies.