In order to ascertain the extent to which Korean college students are familiar with the proper use of the English comma, this study examined all the instances of the comma used in a learner corpus consisting of 787 compositions written by Korean college students. All in all, 5,869 tokens of comma errors were identified and subsequently grouped into five categories of errors: (a) omission, (b) addition, (c) wrong substitution, (d) wrong position, and (e) others. A careful examination of these five types of comma errors revealed that the number of tokens in omission was the highest among the five categories, accounting for over half of all the comma errors, and that the students who received higher scores on their essays were just as likely to make comma errors as those who scored lower, a fact which suggests that students with a higher procifiency of English also need instruction on using the comma properly. These results lead to the conclusion that most Korean students are not familiar with contextual uses of the comma and that teaching the comma should be incorporated into English education both at the secondary and at the tertiary level.