The question of whether acetone can be treated as self-associating is considered. Motivations for considering ketones as self-associating are given, based partially on some of their pure-component physical properties but especially on their phase behavior. It is shown that good vapor-liquid equilibria predictions can be obtained for the mixtures acetone-pentane and acetone-water by considering acetone as self-associating. The justification for this approach is the existence of a vast body of literature and experience in the modeling of associating fluids. Thus, we are able to use existing tools, methods, and models to predict phase behavior in fluids with complex behavior (although traditionally considered nonassociating) without resorting to the development of new models and extra terms.