Idiopathic transient osteoporosis of the hip is a rare condition that was first described in a series women in their third trimester of pregnancy. The clinical course is usually benign and self-limiting. Magnetic resonance is very useful for the diagnosis. Differential diagnoses include avascular necrosis of the femoral head, septic arthritis of the hip, osteomyelitis, stress fractures, primary or secondary neoplastic processes, and referred pain from the spine or genitourinary tract in pregnant women. The authors present a case of idiopathic transient osteoporosis of the pelvis in a young nonpregnant woman with insidious hip pain with no antecedent infection or trauma.