Differential diagnosis of delayed language development in the preschool child at the Readiness Nursery of the New York University Medical School can be shown by three case histories. Diagnosis requires identification of factors involved in the origin and development of the child's language deficit both at the time of diagnosis and at the critical ages for language imprinting. Richard, 3 years 11 months, suffered severe malnutrition and maternal deprivation during the first three years of life due to a mother who was an alcoholic and drug addict. Therapy involved residence in a foster home, a language development program and planned experiences with other children. Kathy, 3 years 2 months, was diagnosed as a case of cerebral injury at 18 months causing verbal expression limited to single words and hyperkinetic behavior. Therapy stressed siezure control, language retraining, and psychiatric help for the family. Romona, 3 years 8 months and the 9th of 11 children, showed poor verbal comprehension, single word speech, and poor fine motor coordination. The child was diagnosed as suffering from a complex of genetic abnormality, prematurity, and chaotic early sensory stimulation. Therapy stressed spatial orientation, fine motor coordination and visual motor functioning, auditory sequencing, and language stimulation. At 5 years of age Romona's behavior approached a normal level. All cases at the Readiness Nursery are evaluated and remediated via an interdisciplinary approach. (DB)