There has been a growing consensus among the educational measurement experts and psychometricians that test taker characteristics may unduly affect the performance on tests. This may lead to construct-irrelevant variance in the scores and thus render the test biased. Hence, it is incumbent on test developers and users alike to provide evidence that their tests are free of such bias. The present study exploited generalizability theory to examine the presence of gender differential performance on a high-stakes language proficiency test, the University of Tehran English Proficiency Test. An analysis of the performance of 2,343 examinees who had taken the test in 2009 indicated that the relative contributions of different facets to score variance were almost uniform across the gender groups. Further, there is no significant interaction between items and persons, indicating that the relative standings of the persons were uniform across all items. The lambda reliability coefficients were also uniformly high. All in all, the study provides evidence that the test is free of gender bias and enjoys a high level of dependability.