A repairable mechanical system (as agricultural tractor) is subject to deterioration or repeated failure. In this study, the regression model was used to predict the failure rate of MF399 tractor. The machine failure pattern was carefully studied and key factors affecting the failure rate were identified in five regions of Khouzestan province. Results showed that different annual use hours (AUH) and maintenance policies affected failure rate. According to the data, the MF399 tractors included in 300-1000 AUH are commonly in a randomized breakdown period within their useful life but these tractors tend to enter the wear out period in the 1200-2000 AUH.
