This paper describes a project which examined the impact of various forms of social work intervention with parents on the functioning of the parents and their preschool children. Subjects were 105 children attending one of two day care centers and their welfare families. Effects of three intervention and two nonintervention conditions were studied. The intervention conditions included two open ended approaches (one supportive, offering direct assistance, problem-solving and encouragement, the other interpretive, aimed at helping the parent understand the nature of his/her experience) and a problem oriented approach which focused on specific problem areas. The nonintervention control group conditions included families who had been offered treatment but could not utilize it and families for whom social work services were not available. Children in intervention and control groups were matched for Stanford Binet I.Q. score, sex and age. Assessments were made (at 5, 12 and 24 months after entry in the program) of the parent-child relationship and the child's development, and parent-child and child factor scores were then intercorrelated. Results indicated that parents in all intervention programs (especially those in the open-ended interpretive group) had higher factor scores on being available, affectionate and communicative. Children in the open ended interpretive condition had higher I.Q. scores at 5 months and 24 months after entry into the program. Follow-up testing at the start of kindergarten and one year after families had left the program showed that treatment children, especially the interpretive group, maintained the I.Q. level seen at the 6-week point, whereas the control groups showed a significant decline. (SB)