This investigation confirms the existence of a home advantage in organized sports; however, it refines and extends that knowledge in a number of ways. The home advantage is most pronounced in the indoor sports of ice hockey and basketball; least so, in the outdoor sports of baseball and football. More effective offensive rather than defensive action is the major factor in the home advantage among all sports. Playing at home or away from home is as strong a correlate of a team's performance as is the average quality of its players. Finally, inferences from the data, as well as more direct observations on audience size and its relationship to performance and outcome, justify the conclusion that the home advantage is almost totally independent of visitor fatigue and lack of familiarity with the home playing area; it is mainly attributable to the social support of the home audience.