In the fields of Corpus Linguistics and Teacher Education, there is a substantial body of research relating to corpus applications in the classroom. However, the majority of such work relates to teacher training in tertiary education. In this article, a research project is described in which corpus training was included as part of a Certificate in English Language Teaching to Adults (CELTA), the popular four-week teacher training programme. Specifically, the project focuses on web-based corpus tools that provide frequency information. Observations and evidence are offered from both the trainees' and trainers' perspectives, and the subsequent analysis reveals a number of trends. Overall, it is argued that corpus tools are a valuable training resource on CELTA programmes in terms of developing language awareness and assisting in lesson planning, but that expecting trainees to use corpus tools during teaching practice remains unrealistic. In the ensuing discussion, practical considerations are provided for the integration of corpus tools into CELTA programmes.