The highly atherogenic lipoprotein(a) [Lp(a)] is significantly elevated in patients with renal disease. It is discussed controversially whether Lp(a) concentrations decrease after renal transplantation and whether the mode of immunosuppressive therapy influences the Lp(a) concentrations. In a prospective study the Lp(a) concentrations before and on average 48 months after renal transplantation were measured in 145 patients. The determinants of the relative changes of Lp(a) concentrations were investigated in a multivariate analysis. Patients treated by CAPD showed a larger decrease of Lp(a) than hemodialysis patients, reflecting their markedly higher Lp(a) levels before transplantation. The relative decrease of Lp(a) was higher with increasing Lp(a) concentrations before transplantation in combination with an increasing molecular weight of apolipoprotein(a) [apo(a)]. That means that the relative decrease of Lp(a) is related to the Lp(a) concentration and the apo(a) size polymorphism. With increasing proteinuria and decreasing glomerular filtration rate, the relative decrease of Lp(a) became less pronounced. Neither prednisolone nor cyclosporine (CsA) had a significant impact on the Lp(a) concentration changes. Azathioprine (Aza) was the only immunosuppressive drug which had a dose-dependent influence on the relative decrease of Lp(a) levels. These data clearly demonstrate a decrease of Lp(a) following renal transplantation which is caused by the restoration of kidney function. The relative decrease is influenced by Aza but not by CsA or prednisolone.