This study evaluates the effects of placement of additional equipment in preschool classrooms on the cognitive, perceptual, and social development of urban Negro four-year-old children. Two Get Set classrooms in each of six areas of Philadelphia were paired for teachers, subjects, physical facilities and equipment. One classroom in each pair was enriched through the addition of materials designed to augment one or more of the following: verbal ability, performance ability, visual perception, auditory perception, and social interaction. Enrichment items included a tape recorder and tapes, a Polaroid camera with film and flashbulbs, puzzle sets, prisms, and Negro dolls and puppets. Pretest and posttest measures assessed cognitive, preceptual, and social development of the children. The findings show that the enrichment significantly altered the classroom environment in the experimental classes. Signs of the alteration were present in the cognitive, perceptual, and social development of the experimental children. However, the control children showed greater gain scores in performance ability. Since both desirable and undesirable effects can result from environmental enrichment, the more extravagant claims for the efficacy of certain play materials should be muted and a properly equipped classroom should not be regarded as a panacea for the problems of disadvantaged children. (WY)