Abstract: Recent research highlights the superior influence of affect over cognition in health decision making. The present study examined the independent and combined effects of two message characteristics that are thought to tap into the cognition-affect distinction: message format (rhetorical versus testimonial) and argument type (instrumental versus affective). In this two-by-two experiment, 81 college students were randomly assigned to one of four health messages discouraging binge drinking. The results indicated that messages containing affective arguments were judged more positively and perceived as more effective than messages containing instrumental arguments. The results further revealed an interaction effect between message format and argument type. Testimonials were more persuasive when they contained affective compared to instrumental arguments. Type of arguments did not influence the efficacy of rhetorical messages. The authors hypothesize and find that instrumental arguments reduce the efficacy of testimonials, because they prevent individuals from being transported into the story, and increase psychological reactance.