Abstract   This study investigates the key factors of lean production system implementation by Egyptian pharmaceutical companies. For this purpose, a research model is proposed showing the relationship between three groups of factors (lean production attributes, external lean practices and managerial factors) and the implementation of the lean production system.   Based on data collected from 157 pharmaceutical companies operating in Egypt, statistical analysis was carried out. The results show that benefits of implementing lean production system, ease of use, perceived compatibility, result demonstrability, customer involvement, competitive pressure and tenure in position and management are key elements influencing the implementation of the lean production system by Egyptian pharmaceutical companies.   The research model developed for this study may assist managers to recognize the importance of integrating contextual factors in the process of lean production implementation. Moreover, the findings of the present study may support managers of manufacturing companies involved in implementing lean production system in identifying and assessing the influence of key factors that facilitate or hinder the successful implementation of lean production within their companies.