The document presents a study examining grammatical errors of non-native English writers in first-year composition courses, focusing on portfolios from ESL students. The analysis identifies the top five errors—word choice, missing commas, articles, tense shifts, and prepositions—highlighting differences between this study and prior research by Lunsford & Lunsford. It underscores the importance of understanding these errors for composition instructors and suggests a potential correlation between mistake frequency and revision efforts.