This article presents two studies based on a corpus of American English speech by and to five children from 2 to 5 years old. The first study investigates frequency of antonym co-occurrence in speakers' turns. The second examines the discourse-functional properties of those co-occurrences, with comparison to adult-directed adult English. We find: (1) children know/use antonyms at earlier ages than experimental studies have shown; (2) children use antonyms for mostly the same discursive purposes as adults do; (3) children can be categorized as being either `heavy' or `light' antonym users, and `heaviness' of antonym use seems to correlate to other aspects of antonym behaviour.