AbstractIn some factories production epochs occur that allow system components to be replaced at reduced cost. Over a long production run the unit cost of replacing these stochastically deteriorating components can be controlled by decisions which govern when production is to be interrupted for component replacement and when components are to be replaced at the reduced cost replacement opportunities. This paper develops and analyses models for optimizing "interrupt and opportunistic" replacement strategies in simple systems. Numerical results are given that illustrate the advantages of combining interrupt replacement with opportunistic replacement.