This study investigates the effect of advertising message involvement (AMI) on brand-related beliefs, attitude toward the ad (Aad), and their corresponding certainty dimensions. Support is found for the notion that belief strength is unaffected by involvement level, though brand-related beliefs are held with greater certainty for high- as compared to low-involvement individuals. Aad was also found to be more confidently held for high- versus low-AMI receivers. However, contrary to expectations, AMI had a direct effect on Aad as well. © 1993 John Wiley & Sons, Inc.