This paper reports the results of exploratory research on reproductive and sexual health knowledge and sexual behaviour of young, unmarried women who migrate to cities from rural areas for work, and their access to and needs in relation to family planning in Beijing, Guangzhou, Shanghai, Guiyang and Taiyuan, in China. Focus group discussions were conducted with 146 young women aged 16-25 and 58 in-depth interviews with key informants. Some of the young female migrant workers were sexually active and living with their boyfriends, most of whom expected to marry each other. Most of the women lacked basic information about reproduction and contraception, and did not know where or how to obtain contraception. There were social, psychological and economic barriers to accessing services. Only a small proportion of those who were unmarried were using contraception, so induced abortion was often the outcome of unprotected premarital sex. Pleasing male partners also played an important role in unprotected sex. The training, attitudes and approach of the entire family planning service system in relation to unmarried and young people in China, including this migrant population, needs to be reorientated so as to provide them with appropriate and adequate services.