This paper reports on an experiment to determine: (1) the effects of two different styles of television program format on the ability of preschool children to recall program content and (2) the cumulative effect of sustained viewing of particular programs upon spontaneous play behavior. Three groups of preschoolers (totaling 58) were exposed to two weeks' daily viewing of either "Misterogers' Neighborhood,""Sesame Street," or a control series of nature and animal films. Hypotheses tested considered whether format differences designed for constructive impact actually yielded such results, and the extent to which format may have special impact due to developmental and personality differences among children. Interactions of child age, sex, IQ and imaginativeness with the stimulus conditions were considered. Results included indications that the slower paced format and other characteristics of the "Misterogers" program yielded positive changes, especially for initially less imaginative children, in imaginativeness of play, positive affect, concentration and social interaction with adults and peers. (BF)