Two patients are presented with rare aseptic osteonecrosis of the femoral head appearing during the last trimester of pregnancy. Both patients suffered from increasing pain in one hip joint, beginning about one month before parturition. Radiographs demonstrated local osteoporotic changes of the femoral head on the painful side. Needle aspiration of the hip joint yielded a scant amount of clear, sterile synovial fluid and gave prompt relief of pain in both cases. The patients' history did not demonstrate any predisposing factors to osteonecrosis other than pregnancy. Treatment comprised omission of weight-bearing on the affected lower extremity for a month or two. The patients had completely recovered one year postpartum, and radiographs were normal.