This paper presents on EMQ model which determines an optimal production run length in a deteriorating machine. It is assumed that a machine is subject to a random deterioration from an in-control state to an out-of-control state with on arbitrary distribution and thus producing some proportion of defective items. An optimal production run length and a minimum average cost are derived in each of three deteriorating processes; constant, linearly increasing, and exponentially increasing. The model with repair cost is also analyzed. Several mistakes in previous research are found and discussed. Numerical experiments are carried out to see the behavior of the proposed model depending on the cost factors as well as machine parameters, and some interesting behaviors are observed.