Despite the widespread adoption of communicative language teaching (CLT) in ESL countries, research suggests that curricular innovations prompted by the adoption of CLT in EFL countries have generally been difficult. The literature on curriculum innovation suggests that teachers' understanding of an innovation is central to its success. A study of a group of South Korean secondary school English teachers' perceived difficulties in adopting CLT reveals that the difficulties have their source in the differences between the underlying educational theories of South Korea and those of Western countries. The results suggest that, to adopt CLT, EFL countries like South Korea will need to change their fundamental approach to education and that implementation should be gradual and grounded in the countries' own EFL situations. In the long run, EFL countries should establish their own contingent of language researchers in order to develop English teaching theories more suitable for their EFL contexts. Change agents must study teachers' perceptions of an innovation to ensure its success.