Researchers in migrant health clinics in Washington state found cost to be the single most commonly reported reason given by foreign-born Hispanic women for never having had a mammogram. The true significance of this finding beyond self-report was unknown. A randomized intervention trial designed to test the effect of fully subsidized mammograms on utilization was conducted within this population. Women in the intervention group received standard clinic instruction plus a voucher for a free mammogram. Controls received standard clinic instruction alone. Eighty-seven percent of women receiving vouchers obtained a mammogram within 30 days, compared with 17.5% of controls. Logistic regression analysis revealed that women receiving vouchers were 47 times more likely to obtain a mammogram than controls. This confirms women's self-report that cost is a major barrier to accessing screening mammograms in this low-income migrant population, and that women are more likely to utilize this service when financial barriers are removed.