An increasing number of manufacturing firms are developing and implementing just‐in‐time (JIT) systems. A unique feature of a JIT system is the new partnership philosophy of the buyer‐seller organizations, which is essential to its successful implementation. This article is based on the results of an empirical study of OEM adopters of the JIT concept. It demonstrates the dramatic effect of the system on traditional buyer‐seller practices, measures the performance results to date, and points up the key role of purchasing and materials management in developing successful buyer‐seller JIT linkages.