An important task that operational managers have is to find the optimal amount of stock and delivery time. The goal of every company is efficient and rational inventory management in order to rationalize and minimize costs and make a profit. The most important item that affects inventory management and overall customer satisfaction is demand. Inefficient inventory management results in high costs and losses for the company. Over the years, many techniques and methods have been developed to optimize and simplify business. The paper presents models for optimal inventory management, while the Just In Time system is explained in detail due to its efficiency, both in inventory control and in labor relations. The objectives of the paper are: to emphasize the importance of inventory management and define inventory management methods, to show the use of Just In Time production system in Toyota's production system, and to show the use of Just In Time system in inventory management on the example of McDonald's restaurant. Manufacturing companies pay special attention to inventory management to reduce costs and keep inventories to a minimum, so the paper presents an example of using Just In Time systems within Toyota's production facilities to try to improve return on investment by reducing inventory in the manufacturing process. Also, the Just In Time method of inventory management is illustrated by the example of McDonald’s restaurant.