Two pairs of brothers, all longterm alcoholics, were observed during periods of experimentally induced intoxication. The clinical study of their interactional behavior was used in the derivation of a model for alcoholism based on a systems approach. Alcohol was used in two very different ways by two drinking systems. In one, it allowed for the controlled release of aggression by engineering a role reversal; in the other, it clarified dominance patterns within the relationship and relieved the tension emanating from an ambiguous reading of the individual roles within the system. In each the end result was the stabilization of a dyadic system which might otherwise be expected to be characterized by chaos.