As part of a population-based intervention to improve periodic mammogram screening, we examined WTP for mammography in five ethnic groups. Through random digit dialing, we contacted households in low-income census tracts of Alameda County, California (San Francisco Bay area). Women who met the ethnicity, age and cancer-free eligibility criteria were invited to participate. For the baseline assessment, women were surveyed over the phone in their preferred language. Of the 1465 surveyed women, 499 identified themselves as African-American, 199 were Chinese, 167 were Filipino, 300 were Latina, and 300 were non-Hispanic white. Bivariate and multivariate analysis showed that WTP varied significantly by ethnicity (P<0.05). We also found that when Filipino and Chinese women had a female relative with breast cancer, they were willing to pay less money for a mammogram. African-American, Latino, and non-Hispanic white women, however, were willing to pay more money for a mammogram if a female relative had had breast cancer. This ethnic difference, when there is a familial link to breast cancer, needs further study as it has implication for genetic testing. Nevertheless, WTP studies that do not account for ethnic differences may be overstating net benefits to society.