In a quasiexperimental demonstration study, screening rates for breast and cervical cancers were measured among Mexican-American women in selected areas of San Antonio and Houston, Tex. This research was primarily designed to evaluate a cancer-screening promotion program in San Antonio by comparing changes in screening rates in panels from the two barrio communities. In a base-line population survey, we found a small, but significant, proportion of women (10%-15%) lacking Pap smears and a larger proportion (30%-40%) lacking mammography. In a panel study following women who lacked screening at base line, there was a trend toward greater Pap smear use among younger women and a significant increase in mammography for all age groups in San Antonio compared with groups in Houston. Although there was a difference in language use between the communities, rates of newly initiated screening within the communities were similar among monolingual Spanish speakers and among those who used English, supporting the hypothesis that the program increased both groups' participation in breast-cancer screening.