Osteitis condensans ilii is one of the rare disease which represents an alteration in the normal bony architecture of that portion of the ilium alongside the sacro-iliac joint: namely condensation without involvement of joint space or adjacent sacrum. We analyzed clinically 9 cases of osteitis condensans ilii who were treated at the Department of Orthopedic Surgery, Medial college of Yonsei University. The results were as follows :l. All patients were women and oldest patient was 47, the youngest 23 years of age. 2. The pain occured following delivery in 3 cases and in one case ofter trauma. There was urinary tract infection in one case. 3. All patients complained low back pain and the pain extended to buttock in 2 cases whereas the radiating pain to lower extremity in 4 cases. 4. In 4 cases was a positive straight leg raising test elicited. 5. In 3 cases the blood sedimentation rate was increased above normal. 6. All patient succeed in relieving pain with conssrvative treatment. In 2 instances steroid was used. 7. There were combined diseases in 4 cases : herniated nucleus pulposus in 2 cases, rheumatoid arthritis in 1 case, osteoarthritis in 1 case.