The usefulness of the Preschool Preposition Test (PPT) as a cognitive screening and diagnostic tool for handicapped children is demonstrated through results of eight independent studies. The subjects were 354 children and youths, aged two to 20 years, with various handicaps: mentally retarded, autistic-like, moderately emotionally disturbed, severely emotionally disturbed, homeless institutionalized, and physically handicapped. The PPT showed statistically significant correlations with other cognitive measures including the Stanford-Binet Intelligence Scale, Peabody Picture Vocabulary Test, Columbia Mental Maturity Scale and Carrow Auditory Test of Language Comprehension. Ratings by teachers on the Classroom Behavior Description Checklist did not correlate with PPT scores, but ratings of mothers' stimulation and nurturance behavior did. When PPT mean scores for the handicapped children were compared with those of the normal standardization sample, scores for the handicapped children were lower at every chronological age except for the emotionally disturbed samples. The PPT has special value for testing otherwise untestable children on abstract thinking and spatial reasoning, for development of new prescriptive programs, and as an added dimension in decisions for special education placement. (Author/CP)