Approximately five million children under the age of 18 will eventually die from smoking-related disease. However, antismoking advertisements directed to adolescents appear to be reducing the prevalence of smoking among youth. The reported study extends prior research using an experiment over time (N= 565) to test the influence of individual factors (grade level, gender, and ethnicity) on the effectiveness of two types of message content in antismoking advertisements. Predictor variables from prior research, such as beliefs about smoking and family and peer smoking, were included as covariates in the analysis. As expected, effectiveness was influenced by individual factors. Long-term health content was more effective among nonwhites, males, and high school students, while short-term content appeared to work better among junior high males.