Relationships between mothers' behaviors and (1) their children's verbal and nonverbal cognitive functioning, (2) their children's level of play, and (3) mothers' perceptions of their children's task motivation were investigated. Forty-four mothers and their preschool children from a wide range of socioeconomic backgrounds participated in the study; there were 25 boys and 19 girls in the sample. Mother-child interaction was observed in the home during the performance of structured tasks and during free play. Following these tasks, children were asked to play with their own toys; during 10 minutes of free play maternal behaviors were observed. Children's cognitive functioning and level of play were assessed at school with the McCarthy Scales of Children's Abilities, and children's play was observed during their regular free play period at school. Mothers' perceptions of their children's task motivation was assessed by means of a 36-item questionnaire: the Mother's Observation of Mastery Motivation. Results indicate that quality of maternal interaction is related to children's cognitive development and to the quality of children's play. Mothers' willingness to give more control to their children apparently facilitates cognitive growth by allowing children greater freedom to explore their environment. Maternal warmth appears to enhance children's ability to organize their play activities in meaningful ways. (RH)