Despite its risks, an increasing number of buyers share design work with their suppliers. However, the outsourcing of design work has been relatively neglected in the literature. Based on mail survey data from 174 U.S. and 122 Japanese automotive component suppliers with product design capability, this study investigates the degree of supplier involvement in design and the factors leading to supplier involvement. The two strongest predictors of the degree of early supplier involvement in design in both Japan and the United States are the degree of technological uncertainty and supplier technical capabilities. Automotive companies are more likely to outsource designs of high uncertainty and select suppliers of high technical capability for design outsourcing, Technological uncertainty also has interaction effects-in the United States, high uncertainty makes customers want to give greater design responsibility to highly technically capable suppliers and those who are most dependent on them as a percent of supplier sales, Overall, the study supports notions of convergence between the U.S. and Japanese supplier management practices in joint product development.