This study investigates the mediating effect of loyalty program membership on the relationship between advertising effectiveness and attitudinal loyalty as well as behavioral loyalty. Data from customers of a retail chain (members and non-members of the loyalty program), are used to test two models that are based on the quality-value-loyalty chain. Findings reveal that for customers who are not members of the loyalty program, advertising effectiveness does not significantly affect either attitudinal loyalty or behavioral loyalty. However, advertising effectiveness affects attitudinal loyalty of members of the loyalty program. Loyalty program membership mediates the relationship between advertising effectiveness and attitudinal loyalty.