Many calcifications due to fat encrosis in the buttocks detected on the pelvis roentgenogram suggest that themajorityof injections intended to be intramuscular actually are delivered into fat. We measured thickness of adultgluteal fat to decide whether the injection using needle of usual length is done into fat or muscle. We measuredthe vertical thickeness of the subcutaneous fat at a point of 2-3cm above the femoral head cut slice with randomlycollected 116 cases of adults in the departement of Radiology, St.Mary's Hospital, Catholic Medical College. Wefound that 32% female cases might actually receive on intraadipose injection when a needle of maximum 3.8cm lengthis inserted into the buttock. If deposition into muscle is desirable, we need to choose needle whose length isappropriate for the site of injection and patient's deposits of fat.