Treatment of adults with acute myeloblastic leukemia has changed substantially over the past two decades. Currently available estimates of survival do not reflect results from present state-of-the-art treatment due to a lag between the availability of new treatments and data concerning their effect on survival on the population level when traditional cohort analysis is used. We estimated trends in age-specific 5- and 10-year relative survival of acute myeloblastic leukemia patients aged over 15 years old for 5-year calendar periods from 1980-1984 through 2000-2004 using data from the Surveillance, Epidemiology, and End Results Program. Period analysis was employed to reveal recent developments in prognosis. Five and 10-year relative survival improved greatly between 1980-1984 and 2000-2004 for all patients except those aged over 75 years old. Improvements were greatest for patients aged 15-34, with increases in 5- and 10-year relative survival of greater than 30% points in this group. Five and 10-year relative survival reached 52.3% and 47.9%, respectively, in this group in 2000-2004. Less pronounced but still substantial improvements in relative survival were seen in the 35-54 and 55-64 age groups. Survival was unchanged, at less than 5%, for patients aged over 75 years old. Our period analysis reveals major improvement on the population level in long-term prognosis of younger patients with acute myeloblastic leukemia, most likely explained by multiple incremental improvements in care including better and more specific diagnosis, improvements in and extension of the use of stem cell transplantation and high dose therapy, and improved supportive care.