Abstract. Cyclosporine is considered to contribute to the high cardiovascular morbidity and mortality in patients after renal transplantation. Tacrolimus may be more favorable in this respect, but controlled data are scarce. In this prospective randomized study in 124 stable renal transplant patients, the effects of conversion from cyclosporine to tacrolimus on cardiovascular risk factors and renal function were investigated. Follow-up was 6 mo. Statistical analysis was performed by ANOVA for repeated measurements. The serum creatinine level decreased from 137 Ϯ 30 mol/L to 131 Ϯ 29 mol/L (P Ͻ 0.01). Three months after conversion from cyclosporine to tacrolimus, mean BP significantly decreased from 104 Ϯ 13 to 99 Ϯ 12 mmHg (P Ͻ 0.001). Serum LDL cholesterol decreased from 3.48 Ϯ 0.80 to 3.11 Ϯ 0.74 mmol/L (P Ͻ 0.001,) and serum apolipoprotein B decreased from 1018 Ϯ 189 to 935 Ϯ 174 mg/L (P Ͻ 0.001). Serum triglycerides decreased from 2.11 Ϯ 1.12 to 1.72 Ϯ 0.94 mmol/L (P Ͻ 0.001). In addition, both rate and extent of LDL oxidation were reduced. The fibrinogen level decreased from 3638 Ϯ 857 to 3417 Ϯ 751 mg/L (P Ͻ 0.05). Plasma homocysteine concentration did not change. Three months after conversion, plasma fasting glucose level temporarily increased from 5.4 Ϯ 1.3 mmol/L to 5.8 Ϯ 1.9 mmol/L (P Ͻ 0.05). Conversion to tacrolimus resulted in a significant reduction of the Framingham risk score. In conclusion, conversion from cyclosporine to tacrolimus in stable renal transplant patients has a beneficial effect on renal function, BP, serum concentration and atherogenic properties of serum lipids, and fibrinogen.During the past two decades, cyclosporine has proved to be a valuable immunosuppressive drug that has contributed to a significant reduction in the incidence of acute rejection after renal transplantation. However, cyclosporine also increases cardiovascular risk profiles (1). Ultimately, up to 63% of renal transplant patients die of cardiovascular disease (2). The increased cardiovascular risk profile as a result of cyclosporine is ascribed to both a quantitative increase in LDL particles and an increased oxidizability of the LDL particles (3-5). Use of cyclosporine is also associated with increased plasma lipoprotein(a) (Lp[a]) (6) and homocysteine levels (7), but these effects are not unequivocal (8). In addition, unfavorable effects on the fibrinolytic system by cyclosporine have been described (9). Apart from these disadvantageous effects of cyclosporine on several metabolic cardiovascular risk factors, cyclosporine leads to an elevation of BP (4). These side effects not only contribute to the high cardiovascular morbidity in renal transplant patients but also may lead to an accelerated loss of graft function (10 -12).Tacrolimus is like cyclosporine, a calcineurin inhibitor, with even more potent immunosuppressive properties. The use of tacrolimus after renal transplantation is associated with a less unfavorable effect on BP and serum lipid levels, but evidence from controlled studies is scarce (4,13). L...