Our positive experience with tacrolimus (FK 506) in heart transplantation has led to our assessing the use of this medication as a primary immunosuppressant in lung transplantation. 62 of our patients after lung transplantation were included in this study. The first 34 patients were treated with cyclosporine A (CyA), the remaining 28 with tacrolimus. No meaningful differences were found in baseline characteristics. The actuarial one-year survival rate was 70.6% for the CyA group and 92.3% for the tacrolimus group. The number of acute rejection episodes per patient was 1.50 for the CyA group versus 1.18 for the tacrolimus group (p < 0.05). The incidence of infection and their spectrum were comparable in both groups. The most frequently reported adverse events were diabetes mellitus 57% (tacrolimus) vs 23% (CyA), and renal insufficiency (27% vs 15%). Tacrolimus seems to be a more potent immunosuppressant after lung transplantation than CyA; on the other hand, diabetes and nephrotoxicity were diagnosed more frequently using tacrolimus. Although our results are very promising, further follow-up on the incidence of obliterative bronchiolitis is warranted.