The differential effects of malnutrition and psychosocial cultural deprivation (PSAC) upon intellectual performance and psychomotor development were studied in 52 preschool children attending nursery schools in urban Santiago (Chile). Nutritional status was evaluated according to Gómez, intellectual performance according to Weschler's scale (WISP and WISC tests), psychomotor development according to the Denver Developmental Screening Test and PSAC according to a numerical scale constructed from maternal I.Q.; socioeconomic status (Graffar) and a psychological questionnaire the correlational analysis, undernutrition was assigned a single value calculated from the severity and duration of the disease. An inverse correlation of - 0.36 existed between malnutrition and intellectual performance, and of - 0.39 between malnutrition and psychomotor development. Also, there was an inverse and significant correlation of - 0.73 between PSAC and psychomotor development; there was no correlation between PSAC and intellectual performance. Verbal I.Q. was more affected (r = - 0.52) than manual I.Q. (r = - 0.18) and children malnourished during the first 6 months of life attained lower scores of I.Q. than normals. The duration of malnutrition (mild in all cases) had no influence upon subsequent I.Q. This study was the basis for a rehabilitation program (educational-nutritional) to be applied in preschool children from nonprivileged areas.