In the automotive industry, Saturn and NUMMI are often touted as exemplars of successful implementation of manufacturing employee involvement. Building on data and extended on-site interviews, this paper explores the differences between the approaches taken at each plant and the relationship between worker involvement and plant performance. Based on this comparison, we offer a model to assess the fit between employee involvement activity emphasis (product development vs. operations improvement) and timescale of the involvement process.MIT's International Motor Vehicle Program and Project Delta at the Sloan School of Management.