A problem is considered of the medium-term planning in an automatic control system (ACS) of assembly production under conditions of random deviations in the dates of delivery of components and in the random level of the demand for final products. A model on the basis of the joint use of the methods of mathematical programming and the optimizing-simulation approach is suggested. This model makes it possible to minimize general productive expenditures that are made up of the expenditures for the storage of components and the penalties for the incomplete supply of finished products.