Many centers determined a significant correlation between post-transplant anti-HLA antibodies production and clinical outcome. In order to confirm this correlation and ascertain the sequential appearance of anti-HLA antibodies, we compared the ELISA (ELISA-PRA) and the anti-human globulin enhanced complement-dependent lymphocytotoxicity panel-reactive antibodies test (AHG-PRA) with the occurrence of acute rejection episodes. Thirty patients who underwent kidney transplantation between December 1998 and October 1999 were assayed. One pre-transplant and 10 post-transplant serum samples were tested from each recipient except from one of them who lost his graft on the 1 week post-transplant. The diagnosis of acute rejection episode was based on classical criteria (fever, graft swelling and tenderness, oliguria, weight gain) and a rapid rise in serum creatinine levels, confirmed by an allograft biopsy graded by the Banff working classification. The 322 pre- and post-transplant serum specimens were tested by AHG-PRA methodology and 298 of them by the ELISA-PRA. The agreement coefficient (kappa) for both methodologies was 0.63. There were 27 acute rejection episodes in 19 patients. AHG-PRA results were significantly correlated (Hazard ratio=10.06; P=0.006) with this occurrence. These data were not confirmed with the ELISA-PRA procedure. Our results suggest that a routine post-transplant AHG-PRA test offers an early risk assessment of acute rejection episodes and may be a useful method for monitoring the kidney transplant evolution.