In competitive markets, customer retention is more efficient than trying to attract new customers. Brand loyalty is an intrinsic commitment to repeatedly purchase a particular brand. But most analyses have been conducted in one specific category only. It has been shown that product purchases in one category depend on purchases in other categories. The aspect of cross-category related brand loyalty has been somewhat neglected so far. We concentrate on cross-category relationships of strong national brands and on how customers' brand choice decisions are related across several product categories.