A study was conducted to develop reliable measures of parents' perceptions or concerns about their children's progress in the domain of peer relations, and to assess the relationship between perceptions of progress and concerns. The study sample consisted of 62 white, preschool children (34 girls and 28 boys) and their mothers and teachers. Participants were recruited from 14 child care centers in Indiana and Illinois. A home visit was scheduled with each family to obtain measures of mothers' perceptions of progress, perceived parental control over the child's behavior, perceived difficulty of affecting change in the child's behavior, and concerns. Mothers were asked to complete a questionnaire about their policies for informal peer play activities in the home, and to report on their child's peer contacts outside of school. Teachers were asked to rate children's classroom social behaviors and peer relations on the Preschool and Kindergarten Teacher Rating Scale. It was found that girls were viewed as being more advanced in peer relations than boys. For both genders, mothers of preschoolers saw their children as more sociable than prosocial. Although the level of concern reported by mothers in the sample was not high, when higher levels of worry were reported, these were more often associated with children's sociability than with their prosocial behavior. Mothers were particularly concerned about behaviors that they saw as difficult to influence and control. Mothers who held a high opinion of their child's sociability worried less, and tended to be more involved in their child's informal play activities, than mothers with lower opinions of their child's sociability. A 20-item bibliography is included. (AC)