HIV/ AIDS transmission is a major threat to married women around the world and especially in developing areas such as rural northern Thailand. Heterosexual transmission is the dominant route by which this disease is acquired. Married women routinely have unprotected sex with their husbands and have limited ability to change this behaviour to protect themselves. Specific intervention is needed to enable married women to take action to protect themselves from HIV/AIDS. The study aims to develop, conduct and evaluate the effectiveness of an HIV/AIDS prevention and intervention program in rural northern Thailand. It used a community development model to enable married women to improve their internal factors of self-efficacy, self-esteem and hope and to increase their behavioural skills for negotiation of safe sex practices and condom use with their husbands. The method was used in which eight villages were randomly assigned to either treatment or control conditions, with the village as the unit of randomisation. The intervention program was delivered by health volunteers and trained as agents of change to motivate and mobilise married women in the program. The intervention was implemented through community mobilisation and a grass roots community-based initiative. Pretest and post-test questionnaires were administered to assess internal factors and behaviour skills among 607 married women aged between 18-49 who were living in the villages participating in the study. The results of the intervention program showed enhanced internal factors among the married women. Most importantly, the number of married women demonstrating ability in negotiation skills increased from 33% to 92%, and the percentage of couples using condoms more frequently increased from 24% to 59%. In conclusion, the trial demonstrated that HIV/AIDS prevention intervention increases married women?s ability to protect themselves against HIV infection. This inexpensive education and skills building package to help the prevention level of HIV/AIDS could be widely implemented throughout Thailand and in other developing countries, which have similar social structures