Annual sales of store brands and retailer introductions of new store brands have grown quickly in recent years. We address retailers' product assortment decisions (in terms of store and national brands) and related pricing decisions at two competing retailers, along with pricing decisions of a manufacturer of a national brand product. Each retailer can offer the national-brand product and a competing store-brand product in the same category. We model the competitive dynamics via a manufacturer-Stackelberg game. The national brand manufacturer first sets a wholesale price (the same for both retailers) and then the retailers engage in a Nash pricing game for the product(s) they choose to carry. Finally, customers, who are heterogeneous with respect to both their loyalty to the retailers and their willingness to pay per unit of quality, decide whether and what to purchase.