Two experiments tested whether the perceived entitativity of groups (i.e., cohesiveness) influences judgments about those groups, in terms of both their observable physical properties and underlying psychological traits. Entitativity was manipulated with groups whose members were similar or dissimilar in skin color. Experiment 1 demonstrated that beliefs about entitativity elicited more accurate judgments of skin color for entitative than nonentitative social groups, although memory for individual members of entitative groups was relatively impoverished. Experiment 2 revealed that entitative groups were viewed as not only physically similar but also psychologically homogeneous and elicited strong negative trait and behavioral judgments. Together, these findings suggest that physical properties (e.g., similarity) can create perceptions of psychological "groupness" that have important consequences for group perception.