This paper investigates the treatment of antonymy in Collins COBUILD Advanced Learner’s English Dictionary (2003) in order to find out what kinds of headwords are provided with antonyms as part of their definitions and also discusses the principles for antonym inclusion in the entries. CCALED includes canonical antonyms such as good/bad and dead/alive, as well as more contextually restricted pairings such as hot/mild and flat/fizzy. The vast majority of the antonymic pairings in the dictionary are adjectives. Most of the antonyms are morphologically different from the headwords they define and typically do not involve antonymic affixes such as non-, un- or -less. Only just over one-third of the total number of pairs is given in both directions. The principles for when antonyms are included in CCALED are not transparent to us. We propose a corpus-based method to support decisions about antonym selection and inclusion.