A validity problem in measuring exposure to mass media campaigns.

Recognition of radio and television messages included in three mass media campaigns designed to keep adolescents from starting to smoke cigarettes was measured in six treatment and four control cities (Standard Metropolitan Statistical Areas) in the southeastern United States. The telephone survey of 574 randomly selected adolescents found high recognition of campaign messages even in the areas where the campaigns had not been broadcast. Campaign messages that differed significantly from other anti-smoking messages were less likely to be falsely recognized. These results reinforce the need to include true control groups in mass media evaluations and to construct distinctive messages if exposure is an important aspect of campaign evaluation.