TO DISCOVER HOW A PERSON'S (P) SELF-CONCEPT IS AFFECTED BY THE CHARACTERISTICS OF ANOTHER (O) WHO SUDDENLY APPEARS IN THE SAME SOCIAL ENVIRONMENT, SEVERAL QUESTIONNAIRES, INCLUDING THE GERGEN-MORSE (1967) SELF-CONSISTENCY SCALE AND HALF THE COOPERSMITH SELF-ESTEEM INVENTORY, WERE ADMINISTERED TO 78 UNDERGRADUATE MEN WHO HAD ANSWERED AN AD FOR WORK IN PERSONALITY RESEARCH. THESE SUBJECTS WERE THEN CONFRONTED WITH TWO OTHER JOB APPLICANTS, HALF WITH "MR. CLEAN" (WELL-DRESSED, WELL-GROOMED, SELF-CONFIDENT), HALF WITH "MR. DIRTY" (JUST THE OPPOSITE). THE SUBJECTS WERE THEN GIVEN THE OTHER HALF OF THE SELF-ESTEEM INVENTORY AND A FINAL QUESTIONNAIRE ASKING FOR THEIR PERCEPTIONS OF O AND OF THE SITUATION. ANALYSIS OF THE DATA LED TO THE FOLLOWING CONCLUSIONS--(1) IN ANY SITUATION (COMPETITIVE OR NONCOMPETITIVE), AN O WITH SOCIALLY DESIRABLE CHARACTERISTICS CAUSES A LOWERING OF P'S SELF-ESTEEM, AND AN O WITH NEGATIVE CHARACTERISTICS CAUSES AN INCREASE, AND (2) IN ANY SITUATION, SUBJECTS WITH A HIGH LEVEL OF INCONSISTENCY CHANGE THEIR SELF-ESTEEM MORE THAN THOSE WITH A LOW LEVEL. THIS PAPER WAS PRESENTED AT THE 1967 MEETING OF THE AMERICAN PSYCHOLOGICAL ASSOCIATION (WASHINGTON, D.C.). (RD)