Abstract: In this paper the writers reported 5 cases of lactic acidosis induced by the use of henformin in diabetics. Among them one patient died because of delayed treatment. Two patients ad severe acidosis with pH 6.87 and 6.89, respectively, and were cured with moderate dosage of odium bicarbonate. The autors suggested that blood gas analysis should be repeated frequently uring treatment and sodium bicarbonate should not be given temporarily if the blood pH was ncreased to about 7.20.