Reparable items, as opposed to consumable items, are usually rebuilt upon removal from service. A reparable item inventory system is composed of an inventory of ready-for-issue (RFI) items and an inventory of non-ready-for-issue (NRFI) items awaiting repair at the overhaul and repair facility. Since not all units issued in RFI condition will be recovered, procurement is necessary to supplement repair and maintain the population of units. This report describes such a system and presents a number of mathematical models, both deterministic and probabilistic, which prescribe the manner in which such a system should be operated. (Author)