The kidney transplant program at the Ospedali Riuniti of Bergamo, Italy was established in 1989. Since its inception, 367 patients have been transplanted, including 357 kidney transplants from cadaveric donors and 10 from living-related donors. Overall 8-year patient and graft survival rates were 94% and 77%, respectively. By 1995 our unit co-ordinated the activity of the Department of Immunology and Clinics of Organ Transplantation, Ospedali Riuniti--Mario Negri Institute for Pharmacological Research, Bergamo. The dual "marginal" kidney transplant program in the same recipient was launched in August 1997, as a part of an international cooperative network which established the "Double Kidney Transplant Group" (DKG). To date, 19 dual kidney transplants have been successfully performed in our center. Four combined heart-kidney transplants and 2 combined liver-kidney transplants have also been performed. During the past 4 years several studies involving conventional antirejection drugs were carried out, particularly focussing our attention on cyclosporine (CsA) through pharmacokinetic and pharmacodynamic approaches: 1) a simplified method to evaluate daily exposure to CsA has been set up; 2) the monitoring of calcineurin activity in whole blood samples was evaluated as a way to optimize CsA dosing. As for the new immunosuppressants, studies are ongoing with mycophenolate mofetil (MMF). We are co-ordinating a prospective multicenter randomized trial of steroid sparing in kidney transplant recipients given MMF or azathioprine as a part of their immunosuppression therapy (MY.S.S. study). This involves 9 Italian transplant centers and 2 European centers. Up to now 325 patients have been randomized. Moreover we have set up an HPLC method for measuring plasma mycophenolic acid (MPA), and examined the possibility of optimizing MMF dosing by drug pharmacokinetic monitoring. Further studies have been addressed to chronic allograft nephropathy. The nature and mediators of renal lesions in kidney transplant patients given CsA have been explored taking into account the gene expression of endothelin-1, RANTES and MCP-1 in graft specimens from patients who had evidence of CsA nephrotoxicity, chronic rejection, or no lesions at histological examination. The impact of percutaneous transluminal angioplasty and stenting of posttransplant renal artery stenosis on renal function recovery was also recently examined. From this study we conclude that the procedure is safe and effective to normalize the functional changes sustained by hemodynamically significant artery stenosis. Moreover, Doppler ultrasound scanning is an useful, reliable, non-invasive tool to monitor the renal function response to artery revascularization. Thanks to the long-lasting co-operation with the Negri Bergamo Laboratories, we had in the past and still have an active program in experimental animals to investigate strategies for transplant tolerance and transplant gene therapy, besides addressing some issues related to the immunological barrier of xenotransplantation.