Abscess of the psoas muscle (PA) is every more frequently observed in recent years. The PA diagnosed in the authors' center over a period of 91 months are presented, analyzing the main clinical features, microbiologic causal agents, risk factors, treatment and the differences between primary and secondary PA. A total of 19 cases of which 14 were secondary PA (73.7%) and 5 primary PA (26.3%) were diagnosed. The main foci of infection of the former were the bone and the genitourinary tract, with intestinal infection being rare. The most frequent clinical data were lumbar pain with possible irradiation to the lower limb, fever, and leucocytosis with neutrophilia. Gram negative and enteric anaerobes were the bacteria most often identified, followed by Staphylococcus aureus and Mycobacterium tuberculosis. In a high percentage of patients (57.8%) a history of immunodeficiency was reported. In regard to treatment, surgical drainage was performed in 5 cases (26.3%), while ten cases (52.6%) were treated by DPCT. Four patients (21%) were exclusively treated with antibiotics. Recurrence was observed in three cases (15.3%) of the DPCT group requiring new drainage. Of all the cases, 18 were cured while one death occurred, being attributed to the underlying tumoral disease of advanced stage. The authors believe DPCT to be a good therapeutic option in both primary and secondary PA, thereby avoiding the risks of major surgery. In the cases with no underlying immunodeficiency the existence of secondary PA should be discarded as occurred in 7 out of 8 cases with no history of immunodeficiency in this series of patients.