We explored the association between immune-related conditions and adult acute leukemia in a study of 624 patients with acute myeloid leukemia (AML), 124 patients with acute lymphoblastic leukemia (ALL), 63 patients with other acute leukemias, and 637 healthy population controls. Common childhood viral diseases were weakly associated with AML and ALL, particularly with early exposure (< or = 5 years of age). Odds ratios (ORs) were elevated for chicken pox and measles at any age, but only the associations with measles were statistically significant [OR = 1.89; 95% confidence interval (CI), 1.40-2.56 for AML and OR = 1.81; 95% CI, 1.07-3.06 for ALL]. There was no association between other infectious diseases, allergies, asthma, or eczema and risk for AML or ALL, although there was a significant association between psoriasis and ALL (OR = 3.23; 95% CI, 1.25-8.30). These results offer little support for either a protective effect of enhanced immune surveillance or a harmful effect from antigenic stimulation in relation to risk for acute leukemia in adults. However, the associations between cancer risk and childhood infectious diseases are intriguing and may warrant additional research.