This study encompassed ethnographic research conducted in one village in Surin Province in which the majority of villagers are Thai - Khmer. The study objective was to create an understanding of the local beliefs about breast cancer and the way these beliefs influence breast cancer preventive behaviors in Thai - Khmer women within the given social and cultural context . The informants were 25 Thai females between 30- 45 years of age. The data was collected over three months and 15 days by living in the community , interviewing Thai - Khmer women, talking to key informants in the village , and non participant observation. It was found that, for the purposes of this study, Thai - Khmer women could be classified into two groups : those who had no preventive behaviors for breast cancer and the ones who had some preventive behaviors. For the women in first group, there were those who had traditional beliefs about breast cancer and those who had modern beliefs related to breast cancer. Women who had the modern breast cancer preventive behaviors tended to hold the modern beliefs on breast cancer. The factors which were also influential in breast cancer preventive behaviors were based on the changing social context, gender- power relation, new set of information and medical discourse. It was recommended that the breast cancer preventive program should be designed to be culturally sensitive and community-based in nature. Rather than based on fear- arousal model.