16 our of 370 acute myeloid leukemias treated between 1964 and 1973 have been in long survival for more than three years. In the first period 1964-1971 the overall remission rate was 20% and 6 patients has a long survival. In the last two years of study, 10 out of 96 patients have more than three years of survival, the remission rate was over 50%. All the cases were slightly proliferative the first group did not recieve intensive chemotherapy and appear as spontaneous long remission, but in thelast patients intensive chemotherapy seems responsible for the good results.