Considerable change in the romantic and sexual behaviours of Asian young people may be occurring as traditionally Confucian societies modernize and increase outside contacts. This study explores the dimensions and context of this change in three sites at different stages in the process of modernization: Hanoi (early), Shanghai (intermediate), and Taipei (later stage). A survey was conducted of 17,016 males and females aged 15-24 in urban and rural settings in three large metropolitan areas. Survival analysis and Cox regressions were performed to explore ages of respondents at key transitions and the significance of differences between two age cohorts: 15-19 and 20-24. Significant differences are found in levels of sexual and other transitions, even within the narrow time span reflected by the age cohorts. The findings highlight the differential impact of modernization on adolescent sexual behaviour as traditional societies undergo social change, and they underline the importance of context in exploring youthful transition.