Prostatitis, the most common urologic disease in men, afflicts between 25% and 50% of all adult men. It is a complex and not well understood condition, partially because of its often obscure pathogenesis. There are four prostatitis diagnostic and treatment categories: 1) acute bacterial prostatitis; 2) chronic bacterial prostatitis; 3) nonbacterial prostatitis; and 4) prostatodynia. This article reviews prostatic anatomy and pathogenesis, as well as diagnostic and treatment categories. This information can assist the primary care practitioner in the identification and management of this common and often puzzling condition.