This paper addresses one of the important dimensions of the experience of youth in contemporary urban Vietnam; that is their sexual practices, behaviour and attitudes. Within a conceptual framework that focuses on sexuality and social change in a modernising and increasingly open society, and based on data collected from ethnographic fieldwork in Hanoi from 1999 to 2004, this paper describes an emerging sexual culture among urban youth. It highlights the emerging trends, issues, and activities which constitute youth sex culture in present-day urban Vietnam. It further argues that the emerging trends in youth sexual culture are reflective of rapid and diverse changes in Vietnamese society as well as the impacts of market reforms on its moral codes, values, and perceptions. There has been a continuation of the ‘traditional’ perceptions of gender roles (particularly the expectation of women to uphold propriety and chastity) and, at the same time, a recognition of the increasingly assertive role of young women in ‘modern’ sexuality and hence of increasing gender equality in this regard. Meanwhile, young Vietnamese nowadays form heterosexual relationships based on both the grammar of love and the grammar of the market.