Thispaperexaminestwo majorgenericfluidmilkadvertising campaigns in New York City during the 1986-92 period Estimates from a time-varying parameter model show that the evolution ofthe impact ofgeneric advertising on fluid milk sales over each campaign followed a bell-shaped pattern. Results also show that the first campaign was effectivefor twice aslongasthesecondcampaignandthat it had a higher peak and average advertising elasticity. These findings may reflect long-term generic milk advertising wearout in the New York City market.