Two studies were conducted with normal preschool and retarded children to examine D. El'konin's theory that condensation of play activity occurs when social human relationships are reproduced in role play. Two types of condensation were hypothesized: reduction of repetition in a manipulation or in a small unit of sequential manipulations, and omission of unnecessary kinds of manipulations. Both studies verified El'konin's theory in normal children as well as in a mentally retarded child. Findings suggested the importance of adults in facilitating the first transitional stage of play activity from mere reproduction of adult acts to reproduction of adult social relationship or role. (CL)