IN THE FIRST STUDY, RANDOMLY SELECTED SHOPPERS IN FOUR SUPERMARKETS WERE INTERVIEWED BEFORE AND AFTER THE POSTING OF SIGNS URGING THEM TO INFORM STORE MANAGERS OF WITNESSED SHOPLIFTING INCIDENTS. THE SIGNS CARRIED DIFFERENT TAG-LINES PLAYING ON FEELINGS OF ALTRUISM ('WE NEED YOUR HELP'<, GUILT ('DON'T BE A GUILTY BYSTANDER'), OR SELFISHNESS ('SHOPLIFTING COSTS YOU MONEY'). IN THE SECOND PART OF THE FIRST STUDY, THE SHOPPERS' RESPONSES TO STAGED SHOPLIFTING INCIDENTS WERE MEASURED FOR THE VARIOUS SIGN CONDITIONS. THE SIGNS WERE NOTICED BY OVER HALF OF THE SUBJECTS IN BOTH THE INTERVIEW AND EXPERIMENTAL PROCEDURES. HOWEVER, THE SIGNS HAD ONLY A SMALL EFFECT ON THE EXPRESSED ATTITUDES OF THE SHOPPERS TOWARD REPORTING SHOPLIFTING AND NO EFFECT ON INTERVENTION BY BYSTANDERS. IN THE SECOND STUDY, THE VARIOUS SIGN CONDITIONS WERE REPEATED IN EXPERIMENTS IN WHICH A SECOND ACTOR CALLED THE SUBJECT'S ATTENTION TO THE STAGED SHOPLIFTING INCIDENT. ALTHOUGH THE PRESENCE OF THE SECOND PARTY TO DEFINE THE SHOPLIFTING SITUATION HAD A STRONG INFLUENCE ON REPORTING, THE PRESENCE OF SIGNS DESCRIBING HOW TO REPORT HAD NO IMPACT. THE RESULTS SUGGEST THAT DIFFERENCES BETWEEN NONPERSONAL (SIGN) AND INTERPERSONAL COMMUNICATION MUST BE CONSIDERED IN DESIGNING ANTISHOPLIFTING CAMPAIGNS. A LIST OF REFERENCES IS INCLUDED.