ESL instructors, curriculum designers, and materials writers must make decisions about which linguistic features to teach and the sequence in which to present them. Historically, ESL professionals have had to rely on intuitions about language use and frequency to guide them in making these decisions. Recently, however, corpus linguistics studies have provided information about the language actually used by speakers and writers in natural situations, including the relative frequencies of features and words. Because more frequent grammatical structures and words will be more useful to students both receptively and in production, this information has great potential for advancing ESL instruction. This article emphasizes the importance of frequency information for the teaching of ESL and offers suggestions for change. In addition, it provides practical applications for teaching certain features and words that corpus linguistics has shown to be quite frequent; their frequency, however, is not yet commonly reflected in materials and practice.