The thesis explores factors influencing birth control practices of Hmong and Karen women according to the National Family Planning Project. These two ethnic groups were the target groups for providing family planning services. It was found that three sets of variables were related to birth control practices. The first one was demographic variables, including age of wife, age of husband, number of sons, number of live children, number of ideal children, need for sons, and need for daughters. The second one was social variables, including ethnicity, residence, opinions on sons’ education, and opinions on daughter’s education. The last one was health variables, including pre-natal care, child delivery experience, knowledge of vaccination, and vaccination status of children. Some variables were not related to family planning but they were related to one another. They included age of wife, ethnicity and vaccination status of children.