This paper provides a taxonomy of errors in the use of English articles by Hong Kong Cantonese ESL learners. A study was conducted with 387 Hong Kong Cantonese ESL learners, including 65 students from three local universities and 322 students from five local secondary schools. They did two free writing tasks of about 200–300 words. Over 600 pieces of free writing were obtained. The use of English articles was analyzed and errors were identified. Irrespective of learners' proficiency levels, similar types of article errors have been observed. While over-extension errors and under-extension errors are both quite common, co-occurrence errors are nearly non-existent. Intended generic reference triggers most problems, although this reference has been least attempted. The function of the noun phrase in which an article error occurs may play a part in error severity, with Object creating most problems for learners, yet the precise effects of noun functions are yet to be determined. It is suggested that more emphasis be put on the teaching of English articles to learners at different proficiency levels. Advanced learners, such as university students, should be engaged in metalinguistic analyses uncovering the subtle differences between the use of different articles in the same linguistic context. Copyright © 2022 De Gruyter.