Serum lipids in 58 renal transplant recipients were related to duration of follow-up, relative body weight, steroid medication, proteinuria and graft performance. Hyperlipidemia was observed between the 4th month and the end of the first year after transplantation in 83% of the patients. Thereafter, the frequency of hyperlipidaemia appeared to decrease: at 4 to 7 years only 61% of the subjects continued to exhibit abnormal high serum lipids. Three mechanisms leading to hyperlipidaemia were identified: 1) overweight, 2) steroid mediation, 3) proteinuria. A forth apparent mechanism was impaired transplant function.