Traditional methods for estimating total body fat rely on the assumption that body fat distribution and bone mineral content are constant. However, in patients undergoing renal transplantation rapid changes in body composition occur, with variations in fat distribution and bone mineral content. In order to determine the reliability of skinfold measurement (SFM) in these patients, we compared it with dual energy X-ray absorptiometry (DEXA), which estimates body composition without reliance on assumptions of constant fat distribution and bone mineral content. Thirty-four adult renal transplant recipients were studied at the time of transplantation and again after 3 and 6 months. The correlation coefficients of DEXA vs SFM at the three time points were 0.84, 0.78, 0.85, respectively (P = 0.0001). In 34 healthy adults serving as controls, the correlation coefficient was 0.95 (P = 0.0001). Total body fat increased progressively following renal transplantation (P < 0.03 by 6 months) with SFM showing considerable disagreement with DEXA measurements of percentage total body fat. Thus skinfold measurements underestimated changes in total body fat following renal transplantation, especially in those gaining substantial amounts of body fat, and DEXA appeared to be a more appropriate technique.