Abstract: The content of ATP in red blood cells has been used as a measure of viability for the evaluaation of storage of blood abroad for several years. At home we completed the determination of ATP in red cells in 32 adult healthy people, using a simple procedure of the fire-fly lueiferase method, we also observed the change of ATP content in red cells during storage. The results showed that the ATP level in red cells decreased, the longer the time the more the decrease. It is suggested that the fire-fly luciferase ATP assay is a simple, rapid, accurate, and reliable method, as a measure of viability, for the evaluation of storage red cells.