Results of the research reported in this paper suggest that the development of mentally handicapped preschool children may not be measurable in distinct cognitive, social/emotional, physical motor, and language areas. This research further indicates that a testing instrument designed to measure the generalized factors of intelligence and social adaptability in a classroom setting may be sufficient for the identification of the mentally handicapped child prior to his (her) first public school experience. This paper highlights the results of an effort to determine the predictive power of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI), the Denver Developmental Screening Test, the Leiter International Performance Scale, the Southeastern Day Care Project (HEW) Rating Scale, and the ABC Inventory when used to diagnose mentally handicapped children in the areas of preschool cognitive, social/emotional, physical motor, and language development. The specific objective of the research is to determine if mentally handicapped preschool youngsters really need to be tested in all four areas of development in order to accurately predict which children require individual help prior to public school kindergarten placement. (Author/DEP)