Social rank theory is a theory of depression and suicidal behavior based on animal models of defeat and entrapment which, in animals result in depressive-type behavior. Gilbert and Allan (1998) have devised a scale to measure defeat. This goal of the present study was to explore the validity and reliability of the Defeat Scale with students of Allameh Tabataba'i University. A sample of 306 (102 male and 204 female) students was selected using simple random sampling. An exploratory factor analysis with varimax rotation was employed. Beck’s hopelessness and depression scales were used to examine convergent validity. Even though the original scale of the questionnaire was published without subscales, the results of the present research identified three subscales labeled inactivity, loser and satisfaction. Together, these three factors explained 63% of the variance of the matrix of item-correlations. The internal consistency using Cronbach’s alpha was 0.91 overall, 0.91 in females, and 0.92 in males. There were significant correlations between Beck’s hopelessness and depression scale scores with scores on the defeat and with the three factor scores. The Defeat Scale has good reliability and validity in Persian culture.