Allograft donations are commonly found to be contaminated. The most of tissue banks has promoted the use of ionizing radiation for the sterilization of biological tissues. The potential for transmission of human infectious diseases and contamination of microorganism has created serious concern for the continued clinical use of hard and soft-tissue allografts. Tissue banks have employed 15-25kGy for sterilization of hard and tendon allografts, which, according to the national standards, approaches the level at which the tissue quality is adversely affected for transplantation. The donations of allogeneic tissues to the Korea Tissue Bank over a 2-year period were reviewed, and the incidence and bacteriology of contamination were detailed. Clinical outcomes were determined for donors who had positive cultures at the time of retrieval and during the processing and they were compared with those of post sterilization. After exposure of the frozen block bone to 25kGy and the processed tissues to 15kGy of gamma irradiation, the authors were able to demonstrate complete inactivation of the bacteria. The aim of this study was to obtain the effects of gamma irradiation and the irradiation dose according to the type of tissue, through conventional microbiologic test without on influence of biocompatibility in allografts. The contamination rate after the final irradiation sterilization is 0% in the processed allografts. This may be due to the fact that the gamma radiation and processing steps are effective to control contamination.