A set of instruments was developed to study children's social networks. Mothers and their preschool-age children were interviewed with regard to (1) the composition of each child's social network and (2) the performance of support functions by network members. To determine the reliability of measures, a pilot sample of mothers and children was interviewed again after 1 to 2 months. Both maternal and child reports of network functioning exhibited considerable stability. Data from the study sample of 60 preschoolers and their mothers were analyzed to evaluate the internal consistency of the measures and the relationship between maternal and child reports of functions performed by network members. Scales derived from the interview data showed good internal consistency. Considerable correspondence also existed between maternal and child reports regarding members of the child's social network. Findings suggested that mothers provide reliable information about the support provided by members of their children's social networks. (Author/RH)