A primary prevention program, the Houston Parent-Child Development Center, directed towards infants and their parents, has effectively reduced the frequency of behavior problems for these children 5 to 8 years after the program's completion. Teacher ratings showed significantly fewer acting-out, aggressive behaviors for program children. Ratings of classroom behaviors found program children significantly less hostile and more considerate than control boys. This appears to be the first primary prevention program to have demonstrated effectiveness in reducing behavior problems over such a long time.