The present study testcd the hypotheses that crowded subjects would evidence higher levels of arousal than uncrowded subjects and that the arousal of crowded subjects would not habituate with the passage of time. In a laboratory setting, subjects were exposed three tinies over a 3-week period to either crowding with physical contact or an uncrowded environment. A high degree of convergence in support of the experimental hypotheses was provided by behavioral, physiological, and self-report measures. Crowded subjects were more physiologically aroused; rated by confederates to be more tense, uncomfortable, and annoyed; and reported more negative affect than uncrowded subjects. No evidence for habituation of. response to crowding was found.