This study examines the impacts of autonomy of dating and engagement on premarital sex among women in Taiwan, utilising a life-course analysis of data from a 1986 island-wide survey. The sample size was approximately 5,000 and the response rate was 86 per cent. Age-specific and cross-sectional analyses show that the transformation of marital arrangements from arranged marriage toward love match, accompanied with a newly developed dating culture and broader perceptions regarding the process of getting engaged and getting married, can explain why the observed increase in, so-called, 'premarital sex' was in fact most likely to occur within a marital context for women in Taiwan.