A central assumption of a combined cognitive response/cognitive structure model of communication is that cognitive responses mediate message effects on belief, attitude, and behavioral intention elements of cognitive structure. This key proposition was tested in a laboratory experiment in which subjects were exposed to advertisements containing varying information about a new brand. The results suggest that either support or counterarguing partially mediate every effect of the ad content manipulations on all three elements of cognitive structure. However, cognitive responses did not mediate all of the treatment-induced variation in cognitive structure. Alternative explanations for the results and issues and directions for future theoretical development and research are discussed.