The study is aimed at knowing the most typical errors of grammar done by the tenth grade students of SMA Yayasan Pendidikan Mulia Jakarta. The writer administers a guide test on writing. Moreover, to differ between errors and mistakes, the writer asked the students to do the same test on the different day. First, the writer corrected the mistakes done by the students by underlying the mistakes. Thus, the errors could be known from the students? mistakes which could not be corrected by themselves. After getting the data, the writer analyzed and categorized the errors based on the grammatical aspects. The study shows that the most typical error done by the tenth grade students of SMA Yayasan Pendidikan Mulia Jakarta is in word choice with percentage 16.98 %. The writer found that the students made this error because they are still confused to choose the right words to make sentences. They have no techniques to produce their own sentences well. Also, the habits in their mother language are influenced them in learning a second or foreign language. Then, the second and the third typical errors done by the students are error in omit a word and spelling with percentages 12.74 % and 9.91 %. The errors mostly made because of their lack of knowledge and experience in learning. It means intralingual transfer and communication strategy are the most typical source of errors.