El-Far and Sobh were the first to describe abnormalities in porphyrin metabolism in Egyptian patients with chronic renal failure (CRF). Our results were confirmed by others. The present investigation aims to study and discuss the nature of those abnormalities and changes in porphyrin metabolism in CRF patients following kidney transplantation. Blood samples and urine were collected from patients (with and without polycythaemia) as well as from normal controls. The activity of heme enzymes such as ALA-S, ALA-D, URO-S, PBGase and URO-D were assayed. Total blood porphyrins as well as enzyme activities such as ALA-S and URO-S were found to be highly significantly increased in all patients, while URO-D activity remained within normal range. The observed elevated erythrocyte porphyrins may be mainly due to increased activity of ALA-S, the rate-limiting enzyme in heme synthesis. The present study is the first of its kind which clearly demonstrates that successful kidney transplantation does not correct or rectify the abnormalities in porphyrin metabolism.