Eleven symptomatic and seven asymptomatic patients, considered to be at high risk of osteonecrosis of the hip, were studied using plain radiography, scintigraphy, computed tomography (CT) with multiplanar reconstruction (MPR), and magnetic resonance imaging (MRI), to determine the precise roles of the various imaging modalities in detecting and staging femoral head osteonecrosis, and to evaluate the incidence in an asymptomatic high-risk patient group. Osteonecrosis was best detected by MRI and was particularly useful for the diagnosis of early disease when other imaging modalities were negative. It is recommended that MRI be performed for the detection of early osteonecrosis, while CT/MPR be used for accurate staging and treatment planning in the established disease.