Market for catfood had been stable for some years. However, with new launches, brand differentiation and loyalty had eroded, increasing purchasing promiscuity. This paper illustrates how advertising can protect share. Arthur's was primarily the weaker brand but it remained steady in spite of increased competition whilst Whiskas, the brand leader proved less resilient. Price, product quality and advertising all had a significant effect on sales. Sales were 21% higher due to advertising, which more than paid for itself.