In our series of 1374 renal transplantations performed between February 1970 and December 2002, we observed 6 cases of infection due to Nocardia asteroides. There were 4 males and 2 females, aged 49.8 +/- 12 years (29 to 63 years). One patient received his first transplantation and the 5 others retransplants. Three patients had PRA > 80%, one 28% and one 40%. One patient was diabetic and two had HCV infection. Two of 6 patients experienced acute rejection episodes. Nocardiosis localisation was pulmonary in 5 cases, cerebral in two and mediastinal in one. All patients recovered after reduction of immunosuppression and appropriate antibiotherapy with trimethoprim-sulfamethoxasole (TMP-SMX). When we analyzed the role of immunosuppression, we observed that only two cases were observed in the 933 recipients transplanted between 1985 and 2002 and receiving cyclosporin, contrasting with 4 cases among 174 recipients transplanted between 1996 and 2002 and receiving tacrolimus. Our data suggest that high immunologic risk patients, heavy immunosuppression, and perhaps tacrolimus-based immunosuppression are risk factors of nocardial infection. Early diagnosis of this severe infection, reduction of immunosuppression and appropriate therapy with TMP-SMX resulted in complete recovery in all our patients.