Investment in flexible manufacturing systems (FMS) and other advanced manufacturing technology is meant to achieve benefits including higher quality products, lead time reductions, less work in process, and a number of other performance outcomes. This paper studies the relationship of productivity performance of FMS as they become more complex. Complexity, within this paper, is measured by the number of numerically controlled machine tools and industrial robots within a system. Productivity analysis is completed using data envelopment analysis with the inputs consisting of complexity measures and the outputs consisting of process/inventory reduction, lead time reduction, unit cost reduction and personnel reduction measures.