Modularproducts refer to products, assemblies, and components that fulfill various functions through the combination of distinct budding blocks, As companies strive to rationalize engineering design, manufacturing, and support processes and to produce a large variety of products at lower costs, modularity is becoming a focus. However, modularity has been treated in the literature at an abstract level, and it has not been satisfactorily explored in industry. Furthermore, the modular technology in electronics such as multichip modules (MCM's) aims at decreasing the average spacing between integrated circuits rather than increasing the variety of product characteristics of other types of designs, This paper develops a methodology for determining modular products while considering cost and performance, To interpret various types of modularity such as component-swapping, component-sharing, and bus modularity, a graphical representation of the product modularity is presented, while the module components of a product set are determined by a heuristic approach, With the module components known, a rule-based fuzzy representation of the module development problem is presented, while the tradeoff between performance and cost of modules is analyzed by a fuzzy neural network approach, The approach is illustrated with the example of an MCM.