To determine the feasibility of heat treating hemoglobin solutions to inactivate viruses, we performed experiments on the thermal stability of this protein and found that the structure and function of deoxyhemoglobin are well preserved during incubation at 60 degrees C for 10 hours at a pH of 7.5. Model viruses and the human immunodeficiency virus were rapidly inactivated under these conditions. The results imply that incubation at 60 degrees C is a practical method for inactivating viruses in hemoglobin solutions.