UNLABELLED Glutathione S-Tranferases (GST) are the enzymes which are strictly specific for epithelial cells of the proximal and distal tubules in the kidney. These enzymes are detected in the urine when some tubular damage process is found. In healthy people urine GST is hardly detected. The goal of this study was to evaluate the release of two isoenzymes -- alpha and pi GST in the urine of kidney graft recipients during the first week after kidney transplantation, aiming to differentiate the cause of the delayed function (DF) of transplanted kidney. MATERIAL AND METHODS 50 cadaveric kidneys were procured using standard technique with "in situ" cooling using UW solution. All kidneys were machine perfused. After preservation kidneys were transplanted to 50 ERSD patients. Standard triple drug immunosuppression was applied (steroids, CsA, Cell-Cept or Aza.). Graft function and the release of alpha and pi GST in the urine were measured 1, 3 and 7 days after transplantation. RESULTS immediate function (IF) was found in 72% (36pts), DF in 28% (14pts). 5 of DF patients had ATN, 4 had acute rejection (REJ) and the remaining 5 had ATN and acute rejection (see table below). CONCLUSIONS High alpha and pi GST concentrations were found in pts with DF graft function during the first 7 days after Tx. Elevated pi GST and low alpha GST in the urine indicates acute rejection. High alpha and pi GST in pts with DF should raise suspicion of graft rejection.