The effect of inventory control on the productivity of manufacturing firms has become topical. Inventory control is an important factor in determining efficiency and effectiveness, thereby achieving productivity of a manufacturing firm. Survival of the manufacturing firms depend on its ability to have uninterrupted production, and effective control of inventory is necessary to achieve an efficient production process. This study was conducted on selected steel firms based in Johannesburg, South Africa. Based on the information obtained from the firms involved, the study established that inventory control has an effect on the productivity of a firm. The study also discovered that inventory control is a problem for larger steel firms compared to small and medium size firms because the larger firms are dealing with big orders. The study also revealed that during the production process, firms tend to use rule-of-thumb when managing inventory control. The survival of the manufacturing firm depends on its ability to have uninterrupted production. Furthermore for the manufacturing firm to be able to achieve an efficient production process, its inventory must be controlled effectively.