An analysis of the credit card fraud problem at Tops pointed out the need for clerks to differentiate legitimate from illegitimate customers in sales transactions. Program initiatives led to the development of a highly successful profile using criteria predicated on purchase traits and the exchange of fraud-related intelligence data with regional departments of the U.S. Postal Inspector's Office and the U.S. Secret Service. Substantial decreases in credit card fraud losses were achieved at Tops, indicating that merchant-based credit card fraud prevention can be effective. An industry-wide prevention effort, however, will be necessary to reduce credit card fraud overall. The most important prerequisites of an effective fraud prevention program seem to include the development of a rational understanding of how the crime is accomplished, the ability to accurately assess what differentiates credit card fraud perpetrators, the establishment of a communications network with relevant external entities, and commitment. 4 references and 1 table