The study is based on the material of acute leukaemia in Norway 1957-81 from the Cancer Registry of Norway. The age-adjusted incidence rates for both sexes have been unchanged. For childhood leukaemias (0-14 years at diagnosis) the age-specific incidence rates have been constant for both sexes and there has been an almost constant incidence for the 5 year birth cohorts 1950-69. Among adults there has been virtually unchanged age-specific incidence rates for most age-groups between 15 and 74 for both sexes. Among those older than 75 years, an increase is seen, most probably due to better diagnostic procedures. No geographic differences were found in age-specific incidence rates.