Single-stage job-shop scheduling has received a great deal of attention in the published literature. Significantly less research has been done in the area of assembly job shops. With the onslaught of MRP implementations designed to plan and control assembly job shops, practitioners have been confronted head-on with the need to improve dispatching procedures. This paper examines the effect of three different product structures on the performance of selected priority dispatching rules in a six-machine assembly job shop. Results indicate that significant relationships exist between the structure of the product bill of materials and the priority dispatching rule, and that specific rules are indeed better suited to certain product structures.