Acute rejection episodes are now as low as 5-20% in the first year after renal 
transplantation; however, graft half-life has remained almost unchanged in the 
last decade. This statistic is mainly attributable to the side effects of 
immunosuppression, with loss of allografts due to the chronic allograft 
nephropathy that is a consequence of calcineurin inhibitor toxicity or 
hypertension. Patient death due to cardiovascular events, infections and 
malignancy also contribute to allograft loss. The introduction of the inhibitors 
of the mammalian target of rapamycin sirolimus and everolimus in renal 
transplantation has increased the repertoire of immunosuppressive protocols 
substantially. They have a different mode of action and a different side effect 
profile (i.e. lower nephrotoxicity, less hypertension and less neoplastic 
potential) than the calcineurin inhibitors. The inhibitors of the mammalian 
target of rapamycin therefore provide an especially promising alternative for 
the maintenance immunosuppression after renal transplantation. This overview 
provides a summary of the current literature on inhibitors of the mammalian 
target of rapamycin, with a special focus on sirolimus.