This study investigated children's acquisition of Hong Kong Cantonese. Method: Participants were 1,726 children aged 2;4 to 11;7. Single-word speech samples were collected to examine four measures: initial consonants, final consonants, vowels/diphthongs, and lexical tones. A two-way ANOVA was performed to examine the effects of age and sex on phoneme acquisition. Results: There was rapid acquisition of initial consonants from 2;6 to 4;6. All 19 initial consonants were acquired by 6;0 (90% criterion): /p-, m-, j-/ were the earliest to acquire; the last were /tsh-, s-/. Final consonants had a different acquisition time from their initial counterparts. Vowels were acquired by 5;0 and diphthongs by 4;0. All nine tones were acquired by 2;6. The main effect of age was significant for all four measures while sex was significant for all except for tone. Common phonological patterns (10%) for initial consonants were: stopping, fronting, deaspiration, delabialization, affrication, and nasalization; patterns with 5'9.9% occurrence were backing, deaffrication, gliding, and dentalization. Conclusions: The acquisition of Cantonese shows similarities with English acquisition yet also had specific characteristics. Factors that contributed to the acquisition rate were functional load, articulatory ease, consonant-vowel (CV) interactions, phonetic variations, and the behavior of vowels and their allophones.