Three approaches of validation enquiry were applied on the data obtained from a proficiency test carried out with 3,398 PhD candidates as a partial requirement for entering PhD program in Iran. The data obtained from the reading section were subjected to an exploratory factor analysis (EFA). The EFA yielded nine factors in the reading section. Furthermore, a design of multitrait-multimethod was also investigated, the traits being grammar and vocabulary and the methods, multiple choice and cloze test. The test demonstrated both convergent and discriminant validity. A third approach was intersubtest correlations as elaborated on by Alderson et al. (1995). For this, different sub-parts of the instrument were correlated with one another and with the total test. The test also showed construct validity as investigated via this approach. It can be concluded that the test had construct validity as revealed by these three approaches.