Asian Americans and Pacific Islanders (AAPI) have the fastest growing rate of overweight and obese children. Aggressive programs are urgently needed to prevent unhealthy acculturation-related changes in diet and physical activity and to promote the healthier aspects of traditional lifestyle habits. We conducted focus groups and key informant interviews to explore knowledge, attitudes, dietary practices, and physical activity levels among three low-income Asian American ethnic groups, Chinese, Vietnamese, and Hmong, in California. Content analysis was used to identify similarities and differences among the groups. Several common health beliefs clearly emerged. Participants noted the importance of fresh (not frozen) fruit and vegetable consumption and physical activity for general health. The concept of good health included having a harmonious family, balance, and mental and emotional stability. All groups also expressed the general belief that specific foods have hot or cold properties and are part of the Yin/Yang belief system common to Asian cultures. The lure of fast food, children's adoption of American eating habits, and long work hours were identified as barriers to a healthy, more traditional lifestyle. A California campaign for Asian Americans using multilevel strategies is recommended to counter the alarming rise of obesity among AAPI youth. Strategies directed to individual, community, and policy levels should emphasize maintenance of healthy traditional diets, informed selection of mainstream U.S. foods, and promotion of active lifestyles to prevent an impending burden from cancer and nutrition-related chronic diseases in AAPI populations. Cancer 2005. © 2005 American Cancer Society.