IN this communication the clinical and antigenic effects of measles vaccine (attenuated) after its administration to several groups of institutionalized children are described and evaluated. The trials were begun in December, 1958, and were continued at intervals until March, 1960.MethodsChildren eighteen years of age or younger, not known to have had measles, were selected for serologic testing to determine susceptibility to this disease. These children were studied in the State Home and Training School, Wheatridge, Colorado, and on the pediatric wards of the National Jewish Hospital at Denver, Colorado. In the State Home about 800 mentally retarded children . . .