The incidence of Reye syndrome has been decreasing in Michigan, perhaps as a result of decreased aspirin use among children. To evaluate possible changes in the frequency of aspirin use, 199 families in Tecumseh, MI, with children younger than 18 years of age were interviewed by telephone in February 1981 and again in February 1983. Based on the reported use of medications for colds or influenza between 1981 and 1983, fewer parents gave aspirin (56% v 25%), but acetaminophen use did not change (59% v 55%). Younger parents and parents who had heard of the association between aspirin and Reye syndrome were more likely to stop giving aspirin. More parents chose to use either no medication or medications containing neither aspirin nor acetaminophen (6% v 32%) for the treatment of colds or influenza. Approximately 90% of parents who chose not to give aspirin for fever also gave medications for colds or influenza that did not contain aspirin. These results suggest that fewer children are receiving aspirin during illnesses that may precede Reye syndrome. The associated decrease in the incidence of Reye syndrome tends to support the hypothesis that the use of aspirin increases the risk for the development of Reye syndrome.