OBJECTIVE Breast cancer is the most common cancer for many Pacific Islander American populations, but virtually nothing is known about the cancer risks and screening behaviors of many specific ethnic subgroups. This paper examines the breast cancer risk, knowledge, attitudes, and screening behaviors of Tongan-American women. DESIGN Research activities were conducted in 3 phases: determination of cancer proportional ratios using data from the California Cancer Registry, exploratory focus groups conducted with 22 women, and self-administered surveys from 303 women (for a response rate of 92%). SETTING AND PARTICIPANTS Survey respondents were Tongan-American women aged 40 years and older, residing in Los Angeles and Orange Counties. RESULTS The breast is the most common cancer site for Tongan women, followed by the cervix and uterus, lung and bronchus, and stomach. The proportion of all cancers accounted for by breast cancer is lower among Tongan women (0.8) compared to White women. We found low rates for all types of breast cancer screening: only 40% of respondents had ever performed a breast self-examination (BSE); 26% ever received a clinical breast exam (CBE); and 25% ever received a mammogram. Many misperceptions existed about breast cancer causes, signs, and symptoms as well as the role of screening in detecting pre-symptomatic cancers. CONCLUSIONS Much emphasis needs to be placed on improving early breast cancer screenings among Tongan-American women, including comprehensive community education, culturally tailored and linguistically appropriate materials, and improved access to low-cost screening sites.