Living donor liver transplantation allows an increasing number of patients with end-stage liver disease the opportunity for effective treatment in the face of a critical shortage of cadaveric organs. Hepatic steatosis decreases functional graft mass and may contribute to graft dysfunction. Screening liver biopsy allows accurate quantitation of hepatic fat, but is an invasive procedure that is not universally employed in the evaluation of living donors. We studied 100 consecutive prospective right lobe living donors, all evaluated with liver biopsy, imaging studies, and various clinical parameters. The accuracy and predictive value of body mass index (BMI) and imaging were compared with biopsy in determining the amount of hepatic fat. There were no complications to biopsy, with 33% showing some degree of steatosis. BMI correlated only weakly with biopsy, with 73% of overweight (BMI > 25) donors having little or no hepatic fat. Imaging was only 12% sensitive to small amounts (5% to 10%) of fat, with increasing sensitivity to more severe steatosis. Imaging diagnosed steatosis in 2 donors without hepatic fat and failed to identify a candidate denied with biopsy-proven 30% steatosis. Conversely, 9% of candidates with BMIs of 25 or less had 10% or greater steatosis. Moreover, three candidates were denied surgery because biopsy detected occult liver disease. Accurate quantification of hepatic fat is not afforded by BMI and imaging studies alone. Screening liver biopsy has a low complication rate and may serve to increase donor safety. Biopsy is essential in identifying donor grafts at risk for poor recipient outcome while maximizing the donor pool.