This study is an attempt to find the relationship between EGP and ESP test in medical field of studies in Iranian context. To do this, four fields of study were randomly selected out of medicine fields. Estimating the mean and standard deviation of the tests, the variance overlap between EGP and ESP tests were calculated. The results indicated that there was no systematic relationship between the students' scores on EGP and ESP tests. In fact the findings indicate that they do not provide similar information. In other words it is not safe to claim that students obtain higher scores in EGP test will receive higher score in ESP test or vice versa in medical field of studies Accordingly, it will be appropriate to accept that EGP and ESP tests have a complementary role in the assessment of the Language proficiency of ESP students.