BACKGROUND: China has one of the most rapidly expanding HIV epidemics in the world with sexual transmission between female sex workers (FSW) and clients accounting for a rising fraction of new infections. Successful HIV prevention relies on the delivery of relevant, culturally appropriate messages to influence behaviour change. However, the cultural systems that give rise to barriers to condom use among Chinese FSW have been poorly examined. A better understanding of these barriers is fundamental to global HIV prevention efforts particularly considering increasing international migration of Chinese women who go on to engage in sex work in their migrant country. METHODS: We conducted semistructured interviews with 23 FSW incarcerated in a re-education and detention centre in Shenzhen, China in July to August 2004. RESULTS: All respondents were internal economic migrants who had entered the sex industry in pursuit of greater financial reward. Respondents explained that they would 'lose face' if they returned from their migration penniless. Women's distinction between commercial and non-commercial partners was very subtle; the nature of 'boyfriend' relationships was diverse and these were often transactional. Condom use was influenced by gender norms, familiarity, a desire to 'save' and 'give' face and, in transactional relationships, whether more money was offered. Women felt HIV was a disease of 'others'; only two women felt personally at risk. CONCLUSIONS: The present study has highlighted the importance of unique cultural structures in Chinese FSW sexual decision-making, an understanding of which will enhance the success of HIV-prevention efforts globally.