The average annual incidence of Reye syndrome reported through national surveillance was lower during 1981 to 1984 than during the previous five surveillance years. This is accounted for by a decrease in cases among children younger than 10 years of age; the number of cases in 10- to 19-year-old persons remained relatively stable during this period. The overall decline in incidence and the differing age-specific incidence trends are apparent for both varicella-associated cases and for nonvaricella-associated cases. During 1985, the incidence has been much lower than during any previous year since surveillance was initiated; this most recent decrease includes children 10 to 19 years of age. Independently conducted surveys suggest that the prevalence of salicylate use for viral illnesses has decreased among children in recent years, particularly among children younger than 10 years of age. The changing epidemiology of Reye syndrome may reflect, in part, the declining use of salicylates among children and teenagers in the United States.