A COOPERATIVE CROSS-CULTURAL STUDY OF ETHNOCENTRISM IS BASED UPON DATA COLLECTED BY ANTHROPOLOGISTS IN VARIOUS GEOGRAPHICAL LOCATIONS. EACH ANTHROPOLOGIST SPENT TWO MONTHS COLLECTING DATA ON TRADITIONAL INTERGROUP RELATIONS, STEREOTYPES, AND HYPOTHETICAL CORRELATES OF RELATED SYMPTOMS OF ETHNOCENTRISM. SOCIETAL AND PSYCHOLOGICAL THEORIES ARE EXAMINED. THE FOLLOWING, RELATED TO SOCIETAL LEVEL THEORIES, ARE PRESENTED--(1) CRITICISM OF THE MIXING OF SOCIETAL AND INDIVIDUAL LEVELS OF ANALYSIS, (2) GLUCKMAN'S ANALYSIS OF THE PROBLEM OF INTERDISCIPLINARY RELATIONS IN SOCIAL SCIENCE RESEARCH AND THE AUTHOR'S VIEW OF THE USE OF LEVELS OF ANALYSIS, (3) PRINCIPLES OF REALISTIC GROUPS-CONFLICT THEORY, (4) THE PREDICTION OF GROUP PROCESSES FROM PRINCIPLES OF INDIVIDUAL PSYCHOLOGY, AND (5) EXTERNAL CONFLICT AND HOSTILITY AS A PROJECTIVE SYMPTOM OF INTERNAL PROBLEMS, RATHER THAN AS A PRODUCT OF INTERGROUP PROBLEMS. SOCIOPSYCHOLOGICAL THEORIES, WHICH ARE DEFINED AS THEORIES EXPLAINING PREJUDICE THROUGH PSYCHOLOGICAL FACTORS OPERATING IN A SOCIAL CONTEXT, CENTER AROUND THE FRUSTRATION-AGGRESSION DISPLACEMENT THEORY. PRINCIPLES UNDERLYING THIS THEORY AND SOCIAL-LEVEL PROPOSITIONS RELATED TO IT ARE DISCUSSED. THIS PAPER WAS PRESENTED TO THE AMERICAN PSYCHOLOGICAL ASSOCIATION MEETING (WASHINGTON, D.C., SEPTEMBER 1967). (PS)