-

The present study investigates how accurately EFL learners assess their understanding of the meaning of unknown words, and whether language proficiency and gender influence their self-assessment. The study was carried out in three phases. In phase one, participants took a proficiency test and read a text in which forty items were highlighted. They were required to assess their understanding of the meaning of unknown words on a four-point scale. In phase two, they provided a translation, synonym, antonym, or an explanation of the unknown words. In phase three, they received the same self-assessment sheet to reassess their understanding of the meaning of unknown words. The results indicated that learners' assessments are not reliable. Moreover, it was found that proficiency in the L2 and gender influence learners' self-assessment. Therefore, on the basis of the findings, L2 learners are encouarged to check the accuracy of their guesses.