Osteonecrosis is common in sickle cell anemia but has been rarely reported with sickle cell trait. Two cases of osteonecrosis of the femoral head caused by sickle cell trait are presented. One patient's diagnosis was delayed because the association of osteonecrosis and sickle cell trait was not recognized. The previous reported cases of this association are discussed, emphasizing diagnostic implications for 12 black patients presenting with hip pain.