Although the diagnostic and therapeutic outcome of renal transplantation has successfully improved during the last decades, acute graft rejection (AGR) is still an ongoing cause of concern being often associated with irreversible graft dysfunction. Renal biopsy remains a valuable tool in the initial assessment of the potential graft malfunction especially during the early post-transplant period. It is an accurate and sensitive means for detecting prognostically relevant microscopic abnormalities, and assisting in subsequent patient management. For long time, the histopathologic evaluation of AGR has suffered from an irreducible bias with poor interobserver rates. Nowadays, the classification schemes of AGR include the BANFF approach and the National Institute of Heath Collaborative Clinical Trials in Transplantation (NIH-CCTT) system: both have been originally designed in order to improve the diagnostic reproducibility of AGR among pathologists. Arteritis and tubulitis, along to clinical information, constitute the cardinal features of the BANFF classification. Distinguishing features of the traditional NIH-CCTT system includes microscopic criteria such as assessment of interstitial hemorrhage, extent and quality of inflammatory infiltrate, and acute glomerulitis, in addition to tubulitis and arteritis. The BANFF classification has apparently gained more popularity than the time-honored NIH-CCTT system since, if used in the appropriate clinical context, it allows a more accurate assessment of AGR, provides prognostically relevant information, and has a better reproducibility rate among pathologists. Nevertheless, the accuracy trend has not significantly improved during the last few years.