Many authors have suggested a pivotal role for Electronic Commerce (EC) technologies in the implementation of Just-In-Time (JIT) replenishment systems. To clarify the relationship between EC adoption and JIT implementation, case studies were conducted with Ford Australia and the Toyota Motor Corporation of Australia. It was found that, while the two companies exhibited many similarities in their adoption of, and attitudes to, EC technologies, there were significant differences in their use of EC to control replenishment from local suppliers. Toyota, the company most committed to JIT supply, was least interested in adopting the standard EC model. The differences are shown to be consistent with, and a natural consequence of, the respective influence of "push" and "pull" principals in the manufacturing philosophy of Ford and Toyota. The findings suggest that the current EC literature presents a simplistic analysis of the relationship between JIT and EC that is implicitly informed by a "push" conception of JIT.