The incidence of physical and psychological aggression was examined for young, at-risk mostly unmarried couples, using reports from both partners and observational data. It was predicted that males higher in antisocial behavior would be more likely to have an antisocial partner, and that antisocial behavior would predict aggression toward the partner. Acts of physical aggression were observed to occur during a videotaped problem solving discussion for some of the couples. The incidence of reported physical aggression was comparable to that found for prior studies. Observed aggression was significantly associated with reported aggression, and psychological aggression was associated with physical aggression. Assortative partnering by antisocial behavior was found. The young man’s aggression toward his partner was predicted particularly by his antisocial behavior, whereas that of the young woman was predicted by depressive symptoms and low self-esteem, along with illicit drug use.