A study investigated 261 Mexican American mothers' estimations of their preschool children's cognitive performance. Existing literature on parental estimations was reviewed. The McCarthy Scales of Children's Abilities (MSCA) were administered to 107 boys and 154 girls, ranging from 32 to 75 months of age. The children's mothers were then asked how they thought their children performed on the MSCA, item by item. At the same session, family background data were obtained and the mothers were interviewed, using a home environmental instrument. Major findings were that mothers tended to overestimate children's performance in general intellectual functioning and between/within MSCA areas; mothers were fairly accurate in their estimations when several accuracy indexes were used; mothers who tended to give higher estimations had more exposure to the culture of schools (e.g., English-speaking rather than Spanish-speaking, United States-born rather than Mexican-born, higher schooling attainment); as mothers' estimations increased, intellectual climate of the home environment increased; and as maternal inaccuracy of estimations increased, children's MSCA performance tended to decrease. The major conclusion was that Mexican American mothers were subject to similar estimation patterns as those observed in the existing literature. Appendices include English and Spanish versions of the maternal MSCA, family data questionnaire, and home environment instrument. (MH/Author)