We present the case of a male patient with post traumatic retroperitoneal fibrosis whose main clinical expression was low-back pain. Diagnosis was established using CAT-scan and MRI, which revealed a large mass of soft tissue that almost entirely enveloped the abdominal aorta. Treatment with 40 mg of prednisone every 24 hours was established. This dose was reduced gradually, and progressive remission of clinical signs and symptoms was achieved, with a significant improvement of subsequent imaging-test results. Treatment was continued for one year. Two and a half years later the patient remains symptom-free, with no recurrence of his condition.