Charles and Miller propose that lexical associations between antonymous adjectives are formed via their co-occurrences within the same sentence (the co-occurrence hypothesis), rather than via their syntactic substitutability (the substitutability hypothesis), and that such cooccurrences must take place more often than expected by chance. This paper provides empirical support for the co-occurrence hypothesis, in a corpus analysis of all high-frequency adjectives and their antonyms and of a major group of morphologically derived antonyms (e.g., impossible, un-happy). We show that very high co-occurrence rates do appear to characterize all antonymous adjective pairs, supporting the precondition for the formation of the association; and we find that the syntactic contexts of these co-occurrences raise the intrinsic associability of antonyms when they do co-occur. We show that via one of these patterns, mutual substitution within otherwise repeated phrases in a sentence, the co-occurrence hypothesis captures the generalizations that were the basis for the substitutability hypothesis for the formation of antonymic associations. 1. Antonymic Association Much current research in linguistics is concerned with textual or discourse bases for