Because of the important role of intra-abdominal fat in predicting increased risk for diabetes, hypertension, and heart disease, methods to quantify intra-abdominal fat are needed. Computed tomography defines quantity of intra-abdominal fat but is associated with significant radiation risk. We explored using magnetic resonance imaging (MRI) to measure amount and distribution of intra-abdominal fat. Because MRI has no known risk, the same subject can be studied repeatedly. Six subjects with percent body fat ranging from 14% to 44% had MRI scans of the chest, abdomen, and thigh on two separate occasions. Total abdominal fat and subcutaneous abdominal fat correlated with percent total body fat as determined from hydrostatic weighing (r = .99, P less than .001). Intra-abdominal fat correlated with the ratio of widest abdominal to widest hip circumference (r = .85, P less than .05). Reproducibility of the MRI measurements of fat was less than 3% for total body areas, less than 5% for subcutaneous fat areas, and less than 10% for internal fat areas. Reproducibility was better in individuals with higher percent total body fat. We conclude that MRI can reliably measure fat areas with no radiation risk to the patient.