This study investigated the frequency of the grammatical errors related to the four categories of preposition, relative pronoun, article, and tense using the translation task. In addition, the frequencies of these grammatical errors in different categories and in each category were examined. The quantitative component of the study further looked at the differences between literature and translation students in the frequencies in different categories. A total of 60 junior EFL students (30 literature and 30 translation), all studied at Shahid Bahonar University of Kerman, participated in this survey. Four translation tests, three in Persian and one in English, were given to the participants to investigate the difficulties of the Persian native speakers learning English. This study showed that the students had the most number of errors in preposition (100.0%), relative pronoun (56.7%), article (25.0%), and tense (6.7%) respectively. The results also revealed that there is a statistically significant difference between the frequencies of the grammatical errors in each category. Furthermore, there is also a statistically significant difference between literature and translation students in the frequencies in different categories. (Contains 13 tables and 13 figures.)