Language anxiety has become a great concern in second and foreign language learning research over the last three decades, and is a topic that triggers significant differences of opinions. As the first theory that emphasises the specific nature of foreign language anxiety, Horwitz, Horwitz, and Cope's theory of foreign language anxiety has been used in quite a number of studies in the field. This paper reviews the theory and discusses the criticisms that other researchers have put forward it with an aim to provide further understanding of the theory for those who are interested in involving foreign language anxiety in their research.