The diffusion of flexible manufacturing systems (FMS) has not only invigorated production systems, but has also given considerable impetus to relevant analytical fields like scheduling theory and adaptive controls. The classical concepts and models may not be adequate to address the issues pertaining to FMS and they may have to be either modified or replaced. One of the important issues in this regard is the performance measures for these systems. These measures are needed for economic appraisals and for system design. Two such existing measures, flexibility and reliability, are re-examined in this paper. A new performance measure, producibility, is introduced here, which is defined as the extent to which a system fulfils its purpose. Appropriate mathematical models are developed to compute this measure for a system. Individual and combined effects of flexibility and reliability on a multi-component, multi-product system are analysed under the framework of producibility.