The authors share results from two longitudinal studies exploring the impact of father's alcohol use on child development. The Michigan Longitudinal Study (MLS) has followed a sample of alcoholic families with 3-5 year old children for 20 years. The Buffalo Longitudinal Study (BLS) has followed a sample of alcoholic and nonalcoholic families beginning when the child was 12 months of age through kindergarten. The two studies independently provide evidence that alcoholic fathers directly and indirectly have negative effects on the social-emotional and cognitive development of their very young children. Fathers' alcoholism alone, or in combination with co-occurring psychopathology (most frequently antisocial behavior), can lead to psychopathology in children as early as infancy.