Though seen with diminishing frequency, psoas abscesses of tuberculous origin are usually secondary to vertebral lesions. The absence of radiologically detectable bone lesions should not exclude the diagnosis, however, as these abscesses can be associated with sub-ligamentary spinal lesions. A case is reported of a psoas abscess of tuberculous origin revealed by a voluminous retroperitoneal mass, without visible signs of any bone lesion. The results of the different examinations conducted are presented.