This study investigated the interface of form and function in the acquisition of negation in Cantonese-speaking children. The data, from the Hong Kong Cantonese Child Language Corpus, were longitudinal spontaneous samples of eight children aged 1;5 to 3;8. The main issues of the study were the sequence of emergence of negative markers mou5, m4 and mei6 and the acquisition trend of 11 semantic categories of negation in children's expressive language. The acquisition trend of the semantic categories matched Bloom's (1970, 1991a) finding that Non-existence preceded Rejection and Denial.