Risk for subsequent development of alcohol problems is not uniform across the population of alcoholic families, but varies with parental comorbidity and family history. Recent studies have also identified disruptive child behavior problems in the preschool years as predictive of alcoholism in adulthood. Given the quality of risk structure in highest risk families, prevention programming is more appropriately family based rather than individual. A family-based intervention program for the prevention of conduct problems among preschool-age sons of alcoholic fathers was implemented to change this potential mediating risk structure. A population-based recruitment strategy enrolled 52 alcoholic families in a 10-month intervention involving parent training and marital problem solving. The study examined the interplay between parent treatment investment and parent and therapist expectations and satisfaction in predicting change in child behavior and authoritative parenting style during the program, and for 6 months afterward among the 29 families whose sustained involvement allowed these effects to be evaluated. Parent expectations at pretreatment influenced their early investment in the program, which in turn predicted child and parenting outcomes. Parent and therapist satisfaction ratings during treatment were associated with one another and with expectations that the program would continue to promote changes in their child. Parent investment was a particularly salient influence on outcome, as higher investment throughout the program was associated with improvement in child behavior and authoritative parenting at termination. Findings indicate that treatment process characteristics mediate the influence of baseline parent functioning on treatment success and that treatment changes themselves predict later child outcomes.