[en] We report 4 patients with surgically proved idiopathic retroperitoneal fibrosis. Retroperitoneal fibrosis was diagnosed correctly in 3 of the patients by computerized tomography. On the computerized tomogram, retroperitoneal fibrosis demonstrated a characteristic soft tissue mass enveloping the vessels and ureters. In 2 patients, the follow-up computerized tomogram revealed spontaneous resolution of the mass in the retroperitoneal space. Computerized tomography is one of the most useful methods in the preoperative evaluation and postoperative follow-up of this disease. (author)