The goal of this two-part study was to identify the perceived influence of sexuality messages from parents, peers, school and the media - four microsystems within the Ecological Model - on emerging adult US college women's sexual attitudes. Findings suggest that parents were the most likely source of the message to remain abstinent until marriage', and participants reported this message as being more influential when coming from school than from the media. The school and the media were the most likely sources of the messages to be safe and use protection' and to use birth control so you don't get pregnant'. College women reported that the message to use protection' influenced their sexual behaviour more, however, when it came from their parents than from school, and more when it came from school than from the media. These results have implications for future prevention programming. Specifically, with respect to these messages, and without generalising beyond these data, parents and school appear to be more influential than peers and the media, and thus should be leveraged in development of new sex education and safer sex programmes.