To the authors' knowledge, little is known regarding the participation of Asian Americans in cancer prevention research. In 2002, the authors mailed surveys to primary care physicians in Northern California to assess their knowledge, attitudes, behaviors, and barriers concerning the participation of Asian-American women in breast cancer chemoprevention research. The response rate was 52.3% (n = 306 physicians). For physician barriers, most respondents selected lack of study knowledge (73%) and effort required to establish eligibility (75%) and to explain risks and benefits (68%). For patient barriers, most physicians chose the following: physicians did not inform patients about trials (76%), limited English proficiency (78%), researcher-participant language discordance (74%), and complex protocols (69%). Significantly more Asian-American physicians than non-Asian-American physicians (but a majority of each) selected as patient barriers a lack of culturally relevant information on breast cancer, a lack of knowledge about research concepts, and fear of experimentation. A majority of Asian-American physicians also selected the following patient barriers: lack of knowledge of preventive care or breast cancer, work concern, misperception that experimental treatment is inferior, personal modesty, and lack of personal benefit. In multivariate analyses, physicians who were in practice longer, who spent more time with patients, or who knew of tools to estimate breast cancer risk were more likely to discuss such trials with Asian-American women; whereas male physicians and those who believed that Asian-American women's deference to physicians was a barrier were less likely to have discussed such trials with Asian-American women. Efforts to increase research participation among Asian Americans should include physician education and linguistically appropriate recruitment efforts.