We describe a series of twelve patients with a psoas
abscess seen in a three-year period in a university hospital and a large teaching hospital in the Netherlands. In our series, five of the 12 patients had a primary psoas abscess. The predisposing conditions were intravenous drug use, diabetes mellitus, prostate carcinoma and haematoma in the psoas muscle in a patient with haemophilia A. Seven of the 12 patients had a secondary psoas abscess. Five cases were due to vertebral osteomyelitis including two cases of tuberculosis. In the other two cases it was due to colitis and urinary tract infection. It is remarkable that in our series there was only one patient with a psoas abscess secondary to a disease of the digestive tract, while this is the most common cause of a secondary psoas abscess in the literature. There were two cases of tuberculosis which is an emerging disease again.