For the prevention of TA-GHVH in patients who received a allogeneic stem cell transplant is mandatory the gamma irradiation of the all cellular blood components. This irradiation is usually done with Cesium 137 and with a special blood bank irradiators. However these devices are expensive; because that, in developing countries, is frequent the utilization of Cobalt 60 and the same device that is used in the radiotherapy department, instead of blood bank irradiators. However the information about the efficiency and safety of this procedure is scarce. We present our experience with this technique. From Dec 2002 to Dec 2005 thirty patients received a allogeneic stem cell transplant and 28 were analysed . The stem cells source was: peripheral blood 25, unrelated cord blood 2, bone marrow 1. The irradiation of the blood components was performed with Cobalt 60 1.24 Mev- (theratron 780 C); the irradiation field was calculated for covering all of the bag surface and a dose of 3.5 Gy was administered to the mild plane of the bag. 158 blood concentrates were transfused, 68 red cell (X:2.5 per patient), and 90 platelets (3.2 per patient). The pre transfusion median hemoglobin and platelet levels were 7.63 g/dl and 12.000/ul; after transfusion was a median increase of 2.3 gm/dl (0.6-4.7) in hemoglobin and 18.000/ul (0-140.000) in platelets. There was no any case of TA-GVHD. Four patients developed pos transplant aGVHD, in all of the cases the disease began 50 days or more after the last transfusion , there were no pancytopenia and the aGVHD was resolved completely with the treatment. Conclusion: In receptors of allogeneic stem cell transplant the gamma irradiation of blood components with Cobalt 60 and the same device wich is used for patients radiotherapy is 100% effective and safe in the prevention of TA-GVHD. This is a very good alternative in centers without a blood bank irradiator.