CROWDING IS DEFINED HERE AS THE PHYSICAL SITUATION OF HIGH DENSITY. THE NEGATIVE EFFECTS OF CROWDING ON ANIMALS ARE SUMMARIZED AND THEORIES SUCH AS TERRITORIALITY AND THE HOMEOSTATIC THEORY REVIEWED, WITH EMPHASIS ON THE QUESTIONABILITY OF MAKING GENERALIZATIONS FROM ANIMALS TO HUMANS. THE HUMAN SPHERE IS INVESTIGATED, AND SPECIFIC STUDIES ARE CITED THAT EXAMINE CROWDING AND CRIME, PERSONAL SPACE AND ISOLATION, AND THE RELATIONSHIP OF CROWDING, AGGRESSION, AND SEX. IN GENERAL, THIS RESEARCH PROVIDES NO EVIDENCE THAT HIGH DENSITY IS BAD FOR PEOPLE. MOREOVER, IT DEMONSTRATES THAT PEOPLE CAN EXIST UNDER VERY CROWDED CONDITIONS FOR A CONSIDERABLE AMOUNT OF TIME WITHOUT BREAKING DOWN AND THAT CROWDING DOES NOT INFLUENCE TASK PERFORMANCE. EXPERIMENTS SHOW PATTERN INCONSISTENCIES IN MALE AND FEMALE REACTIONS IN STUDIES OF DENSITY AND AGGRESSIVE BEHAVIOR, FOR WHICH THE DENSITY-INTENSITY THEORY OF CROWDING IS POSTULATED. THIS THEORY STATES THAT WHATEVER THE INTERPERSONAL SITUATION, HIGHER DENSITY WILL CAUSE THE INDIVIDUAL'S REACTION TO BE STRONGER, ELICITING STRONGER POSITIVE REACTIONS IN POSITIVE SITUATIONS OF GREATER DENSITY, AND PRODUCING MORE NEGATIVE REACTIONS TO NEGATIVE SITUATIONS UNDER HIGH DENSITY. THE MODERN LOCUS OF HIGH DENSITY LIVING, THE CITY, IS CHARACTERIZED, AND RECOMMENDATIONS ARE MADE FOR CITY PLANNING AND DESIGN TO ENHANCE LIFE UNDER INEVITABLY CROWDED CONDITIONS. APPENDIXES CONTAIN TABULAR DATA FROM EXPERIMENTS CONDUCTED. NOTES, A BIBLIOGRAPHY, AND AN INDEX ARE PROVIDED. (MRK)