Manufacturing businesses have been contributing to energy consumption, pollution and resources consumption. Alongside governmental legislations, there are many drivers of Sustainable Manufacturing such as social and market pressures which are growing as awareness about environmental issues increases. These drivers have been extensively researched as evidenced in the literature. However, this study goes beyond the drivers themselves to unveil the factors that underlay each driver. For example, customer demand is a driver that depends on factors such as the importance of environmentally-friendly products to win orders and the bargaining power of customers. Thorough understanding of these factors will provide the knowledge economy with the information required to advance manufacturing and the environment. In this study we analyzed ten factors that underlay the drivers: Market pressure, Competitiveness and Supply Chain pressure. Using data collected from 36 manufacturing companies, factors were ranked based on their importance. The results show the ranking of ten factors. Further analysis of the factors revealed some interesting characteristics of Sustainable Manufacturing.