The increase of survival in patients with Hodgkin's disease (HD) has made appear the problem of secondary neoplasms, included acute leukemias. The authors evaluate the incidence of acute leukemias in 205 HD with a follow-up more than 12 months (mean 92 months). With regard to these latter, 18 (8.7%) were treated with radiotherapy alone, 69 (33.6%) with chemotherapy alone and 118 (57.5%) with a combination of radiotherapy and chemotherapy. Chemotherapy consisted of 2-12 courses of MOPP alone or in combination with ABVD. The relative risk of acute leukemias is 96.7 (CI 95%: 44.2-183.6): nine cases against an expectancy of 0.093. The risk changes during five-years periods, but not significantly, and it not declines after ten years from the diagnosis. Only the alkylating chemotherapy seems to be important to favour the onset of acute leukemias. Among the patients who received a number of courses of MOPP less or equal than 6 (177), seven developed an acute leukemia (relative risk 85.3; CI 95%: 34.3-175.9); among those who received more than 6 (9), two developed an acute leukemia (relative risk 333.3; CI 95%: 40.3-1204.1). Neither the addition of radiotherapy nor the stage nor the splenectomy nor the histotype favour the onset of acute leukemia.