Social cognition is an important component of children's social adjustment. Mental models of relationships, specifically representations that arise through the attachment relationship with parents, and parenting quality are hypothesized to be critical components of social cognition. However, little research has addressed how early attachment representations and parenting quality interact to inform the quality of children's social cognition in the preschool and early school years. This dissertation examined longitudinal predictors of the quality of children's social cognition (defined by negative attribution biases, social problem solving, and loneliness), focusing on how the attachment representation developed in the infant and toddler years, quality of parenting in the preschool and early school years, and exposure to maternal depression interact to influence children's social cognition at 4 1/2 years and at the end of first grade. Both concurrent parenting and children's attachment security contributed to social cognition at 4 1/2 and at the end of first grade. Children's relevant and socially competent solutions to social problems were related to attachment and concurrent maternal depression at 24 and 36 months, while children's negative attributions at 4 1/2 years were related to attachment security at 36 months, but were not related to either attachment at 24 months nor to concurrent parenting. Children's feelings of loneliness, assessed in first grade, were related to attachment at 24 and 36 months, and to concurrent maternal sensitivity. Children's negative attributions were related to attachment and concurrent harsh parenting, while children's aggressive responses to social problems were not related to attachment but were related to concurrent maternal sensitivity and depression. The effects of attachment on social cognition varied according to the parenting received in the preschool and early school years; children with insecure attachment histories were more sensitive to the effects of parenting later in life than children with secure attachment histories. Results point to the importance of parent-child relationships for children's social cognition, and demonstrate the complex origins of social cognition in young children. (author abstract)