A participative goal-setting and feedback intervention increased cashiers' identification-checking behavior at a large grocery store. The cashiers' identification-checking percentages increased from 0.2% at baseline to 9.7% during the intervention phase and then declined to 2.3% during withdrawal. At the control store, the percentages of identification-checked purchases were 0.3%, 0.4%, and 0.7%, respectively, during the A-B-A phases at the intervention store. A comprehensive social-validity assessment showed ID-checking to be accepted by both cashiers and customers. (Contains 2 tables, 1 figure and 2 footnotes.)