The article presents notes by the author on various considerations for making product combination decisions. There are many accounting techniques and concepts-direct costing, break-even analysis and the contribution margin concept which are pertinent to the problem of product combinations. These concepts certainly furnish a starting place in making managerial decisions, however, each of them is quite incomplete in itself. In the development of a model for product combinations which might utilize accounting data, one starting point is to examine the literature of economics. Marginal analysis, as used by the economist, can be applied to the problem of the best combination of products. A correct knowledge of joint and by-product costs is that they serve as a means of regulating production. Although in many cases it is quite difficult to control the quantity of joint products and by-products manufactured, a decision can be made as to whether or not additional labor and materials are to be expended on the newly created joint products and by-products.