Past research has indicated that three-person groups are more likely to produce isolates than two-person groups, with isolates experiencing the greatest difficulties, least confidence, and most intense crowding stress. The present study extended these findings by examining the role of coalition formation as a mediator of social density in three- and four-person groups using a survey technique. As expected, coalition formation between two roommates, resulting in one or more isolates, was more likely to occur in three-person than four-person groups. Consistent with previous research, isolates in both three- and four-person groups reported more crowding, more somatic complaints, dissatisfaction with room and roommates, difficulty in maintaining control, and less confidence in their ability to regulate social interaction than nonisolates. Tripled isolates, however, consistently reported more significant feelings of not being understood by roommates and loneliness, as well as greater exclusion from group decisions, more extreme difficulties in maintaining control and regulating social interaction, and more intense crowding stress. Counterintuitively, with an increase in group size from three to four, reported crowding stress did not increase. Implications for group dynamic processes in ameliorating some of the problems associated with crowding stress are discussed.