Abstract The ability of a manufacturing system configuration to satisfy production demands depends on its availability. The use of the Universal Generating Function (UGF) for evaluating the availability of multi-state manufacturing systems capable of producing multiple-parts is proposed. A generalization of the UGF is introduced in order to deal with multiple types of output performance. This allows considering multiple production rates corresponding to the different parts produced by the manufacturing system. A case study is presented to illustrate the use of the generalized UGF technique in assessing and comparing manufacturing system configurations based on availability.