Summary This report describes two American studies in which 48 male college students and 144 male high school students, respectively, were assigned to high or low spatial density conditions and instructed to construct, as a team, an erector set model within a 40-minute period. High school students were assigned to high, middle, and low attraction groups on the basis of their ratings of their fellow classmates. The results indicated that subjects in both studies did not find those crowded conditions to be aversive or stressful or to influence their affective ratings of their fellow subjects. In the second study, while density had no main effects on task performance, under middle attraction conditions performance was impaired as a function of density. These findings suggest that while crowding did not necessarily result in a stressful experience, both social and spatial elements were important in obtaining optimal group productivity. Overall, negative, and neutral verbal behavior increased as a function of density. Neutral verbal behavior increased in high and middle attraction groups, while it slightly decreased in low attraction groups as a function of density. There were no effects of density and attraction on positive verbal behavior. It appears that crowding intensified social interaction in a negative manner, supporting the contention that crowding can have detrimental effects on human behavior. Crowding should be dealt with as a multidimensional concept that interacts with different settings, individuals, and activities.