This study investigates tone mergers in the Cantonese spoken in Hong Kong, Macao, and Zhuhai. From these three cities, 150 native Cantonese speakers were recruited, stratified by gender and age. Acoustic analyses show that Hong Kong Cantonese and Macao Cantonese are actively merging T2[25] and T5[23], T3[33] and T6[22], thus becoming similar to Zhuhai Cantonese in tonal inventory. The social motivations of the changes are attributed to contact among these Cantonese-speaking communities as well as their contact with Putonghua. Responses to a questionnaire on language use in different domains shows the spread of Putonghua in Hong Kong and Macao and seems to correlate with the advance of the tone mergers. More specifically, the spread of Putonghua in Hong Kong seems to be rolling back the effects of Cantonese standardization, as shown by the tone mergers in the youngest generation in Hong Kong.