This paper reports empirical evidence of the implementation patterns of JIT purchasing developed by the Spanish auto components industry. An analytical framework distinguishing between operational practices, inherent in JIT environments, and complementary practices, characteristic of partnership sourcing arrangements, is proposed and used to guide the study of a sample of 150 manufacturers. Three stages of implementation are identified and the analysis of companies at each stage reveals that size and international presence are key factors. Furthermore, there seem to exist important synergies between JIT purchasing practices which make a holistic implementation more beneficial than the isolated introduction of selected practices.