We explore the use of shopping lists as an external memory aid to consumers' grocery shopping by examining the factors that influence the content ofconsumers' shopping lists and the effectiveness of shopping lists as external memory aids. We analyze the shopping lists and actual purchase behavior of a panel of consumers during multiple grocery shopping trips conducted over a 2-month period. Our results indicate that consumers record on their lists approximately 40% of the items they ultimately purchase. Consistent with the external memory literature, we find that consumers write items on their shopping lists for which there are financial incentives to remember ( e g , manufacturers' coupons), need-based incentives to remember (e.g., the product is frequently used), and schema-based advantages to remember (e.g,, items purchased on fill-in trips). More than 80% of the items written on the shopping list were actually purchased. Thus, shopping lists appear to be an effective external memory storage device for grocery purchasing. We discuss these and other findings in relation to the literatures on external memory and planned versus unplanned purchasing.Consider the following two grocery shopping scenarios. h i e is about to embark on a trip to his local supermarket to pick up several items his family needs for dinner that evening. Before he leaves for the store, Amie's wife gives him a shopping list of the items she would like him to purchase: lettuce, tomatoes, cheese, milk, and Coca-Cola. When Arnie arrives at the store, he purchases the lettuce, tomatoes, and milk. He decides to purchase Pepsi Cola instead of Coca-Cola because the store is having a sale on Pepsi. Arnie also decides to buy some potato chips, some ice cream, and some chocolate bars. Arnie forgets to purchase the cheese.Ruth, another consumer, is also about to go grocery shopping. Ruth needs to purchase many items this week, so she first writes out a shopping list before she goes to the store so she will not forget to buy any items. While putting her shopping list together, Ruth checks her cabinets to see what products she currently needs or will soon be out of. She also checks retail grocery advertisements to find out what is on sale at her local supermarket. Ruth also checks her coupon file for manufacturers' coupons for products she might buy. Once in the store, Ruth makes sure she purchases every item on her list by crossing out each item as she puts it into her shopping basket. The store is out of one sale item that is on Ruth's list. Before she leaves the store, Ruth goes to the service desk to get a rain check for the sold-out item.Consumers like Ruth and h i e presumably create and use shopping lists as an aid to help them while grocery shopping. As summarized in a recent Wall Street Journal article, shopping for grocery items has become an increasingly complex task (Narisetti, 1997):Today's average consumer, more often than not a woman, takes just 21 minutes to do her shopping-from the moment she slams her car door in a supermarket parking ...