Although its historical significance is well established, Mycobacterium tuberculosis today is considered an extremely rare cause of psoas abscess. Nontuberculous bacterial infection, most commonly secondary to an intraabdominal process but at times appearing without an identifiable source, is responsible for the vast majority of psoas abscesses. The recent resurgence of tuberculosis may portend another change in the etiologic trend of psoas abscess. It is essential that the emergency physician not only recognize the potentially subtle presentation of psoas abscess, but also include tuberculosis in the differential diagnosis of infectious causes of this entity. A case of tuberculous psoas abscess in an HIV-negative man is presented. A review of the anatomy, pathophysiology, clinical presentation, epidemiology, and treatment follows, highlighting the similarities and differences between tuberculous and nontuberculous psoas infection.