In an attempt to determine the relationship of situational variables to judgments of crowding, 40 male and 40 female Ss were instructed to place wooden figures in model rooms until they believed the room was crowded. Eight situations were tested, each being related to the variables of degree of acquaintance, situation type and activity type. Specific hypotheses were: a) situations in which the participants were assumed to be acquainted with each other would produce a greater number of model placements than situations involving strangers; b) situations in which the participants were interacting would accommodate a greater number of placements than situations involving an independent activity; and c) a recreational activity would produce a greater number of placements before being considered than a work situation. The results confirmed all of the hypotheses. Many approaches have been taken to determine the effects of on behavior. Calhoun (1962) examined the effects of over-population on rats and found extreme negative effects associated with high density populations: high infant mortality rates, small litters, inadequate nest building, abandonment of young, cannibalism, and abnormal behavior. Defining crowding as an increase in the intensity of competition for space, Christian (1963) tested the effects of on the biology of rats and woodchucks. When crowded rats gave birth, the litters were smaller and the animals weighed less, fewer infants