1. 목적 · This paper provides a comprehensive review of the inventory models focusing imperfect manu-facturing setup and work-in-process inventory. Optimum lot sizes are calculated based on average cost minimization. 2. 연구설계/ 방법론/ 접근방법 · Totals cost function has been defined for all the developed models with assumptions and notation. Optimum lot sizes are calculated based on average cost minimization using a simple algebraic approach. Imperfect manufacturing setup processes are varied from a perfect condition to an im-perfect manufacturing environment in order to get the lot as per the desired scenario. The results obtained using new algebraic approach remain the same as obtained previously. 3. 연구결과 · Developed models are analyzed regarding model sensitivity for different parameters. Parameters include setup cost, demand rate, manufacturing time, rework percentage, rejection percentage and inspection time required for product qualification. A numerical example has been used to analyze models for these several parameters. Setup cost, demand rate, manufacturing time, rejection per-centage and inspection time remain significant parameters and its impact on lot size was considerable. The response of the developed models (GTOQ, GTOOR, and GTOOIR) varies based on their assumption and problem condition. GTOQIR model can be considered more robust and flexible as it acconm1odate more practical working conditions. 4. 실무적 시사점 · These findings are of great value to the manufacturing engineers working particularly in group technology imperfect manufacturing environment. These models can be used to get the optimum lot size at average cost minimization taking process imperfection like rework, rejection and in-spection time etc. Managers will be able to dig out the hidden process imperfection effect on in-ventory lot size 5. 독창성/ 가치 · Economic order quantity and production order quantity models (EOQ and POQ) are based on the unrealistic assumption that process produce good quality product every time. Also almost all proc-esses are facing quality related issues in general and manufacturing setups in particular. This give an insight to manufacturing engineers to consider work-in-process inventory and focus on process behavior regarding product quality to get minimized the total average cost.