As a mixed method research, this study investigated the effect of assessment literacy as well as the impact of experience, academic degree and gender on ESP teachers' use of alternative forms of assessment. To this end, 106 ESP teachers (74 males and 32 females, 77 Ph.D.s and 29 MA/MS.s) completed a multiple-choice 35-item Classroom Assessment Literacy Inventory (CALI) developed and validated by Mertler (2002). To triangulate the data, 32 ESP teachers attended a semi-structured interview in addition. The results of descriptive statistics indicated that 'observation', as one form of alternative assessment, was used most frequently be ESP teachers. The results of Independent-Samples t-test showed that EWSP teachers' assessment literacy had a significant effect on their use of alternative forms of assessment. However, the results of one-way ANOVA indicated there was no significant difference among high-experienced, mid- experienced, and low- experienced ESP teachers regarding their assessment literacy. Moreover, the result of Independent-Samples t-test showed that there was no significant difference between male and female ESP teachers regarding their assessment literacy. Furthermore, the results of Independent-Samples t-test indicated that ESP teachers who held Ph.D. had higher levels of assessment literacy compared to their MA.-holding counterparts. Also, the results of interview revealed that the main reasons for ESP teachers' not using alternative assessment were 'overloaded classes' and 'lack of knowledge of alternative assessment'. The finding of the study and the factors determining assessment literacy are discussed in the paper. Keywords: assessment literacy, alternative assessment, ESP teachers, gender, experience, academic degree
