This study analyzed the errors in Korean high school students' responses to the four writing items of the National English Ability Test (NEAT) Levels 2 and 3. To two Level 2 items and two Level 3 items 1,119 responses were randomly selected and coded based on the error scheme that was developed for this study by adapting some previous studies. The result indicates that some types of errors were more frequently observed in the responses to certain types of questions of the NEAT. Errors in verb tense and aspect, for example, were more frequently observed in question number 1 of NEAT Level 2 and in question number 4 of NEAT Level 3, while article and preposition errors occurred more frequently in question number 3 of NEAT Level 3. Based on a careful investigation of the students' responses to each question, certain characteristics of each question seem to induce certain types of errors more than other types. Question number 1 of NEAT Level 2, for example, requires test takers to narrate or describe past events or experiences; this might cause more errors in the use of verb tense and aspect. The pedagogical implications of the findings are discussed in terms of teaching English writing to Korean students.