This research investigates how a price promotion on a fast-moving consumer good influences the sales of substitute products in a retail shelf or online display. An analysis of supermarket yogurt data finds that when nonpromoted products are strong substitutes for the promoted product, a 1% decrease in the price of the promoted product results in a .25% decrease in the sales of proximal products but no change in the sales of distal products—a negative promotion-proximity effect. However, when nonpromoted products are weak substitutes for the promoted product, a 1% decrease in the price of the promoted product results in a .10% increase in the sales of proximal products but no change in sales for distal products—a positive promotion-proximity effect. Subsequent studies show that these effects occur because a proximal strong substitute is more likely to enter a consideration set with the promoted product (negative promotion-proximity effect) and a proximal weak substitute is more likely to be seen and considered by a consumer who is not interested in the promoted product (positive promotion-proximity effect).