Acute rejection has been identified as the main cause of renal graft dysfunction during the first year after transplantation; it is associated with chronic structural and functional damage, which causes loss of graft and decrease in patient survival. We performed a retrospective and descriptive research consisting in a review of the final reports of biopsies performed due to renal graft dysfunction during the postransplant period. Patients included were transplanted at the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNSZ) from January 2007 to December 2011. A total number of 223 patients underwent renal transplantation during the period considered for this study purpose, 222 biopsies were performed due to renal graft dysfunction in 118 patients (52.9%). 74.5% of patients developed graft dysfunction in the first year after transplantation. The main histopathological findings reported were immunologic events in both living donor (LDRTR) and deceased donor renal transplant recipients (DDRTR), borderline changes were the most common diagnosis. The median time to detect immune events as cause of dysfunction was shorter for DDRTR and they tend to occur in the first 4 months after transplantation. We observed an incidence of 11.8% for acute rejection in the first year after transplantation for LDRTR and 17.4% for DDRTR. Further studies are needed to determine the causes of immunological events and their implications in the evolution of renal graft and patient's survival.