AbstractIn this paper we model a single-base multi-indentured repairable item inventory system. The base has a maximum number of identical on-line machines, and each machine consists of several module types. Our objective is to calculate the steady-state operating characteristics of the system. The usual Markovian approach leads to multidimensional state spaces that are large even for relatively small problems. Solving such a multidimensional system is very difficult because of the huge number of states. Consequently, we propose an approximation technique that allows us to solve large problems relatively quickly. Although the resulting solution is only approximate, a variety of test problems indicates that the algorithm is quite accurate.