• The influence of sociodemographic factors on the initiation of breast-feeding was evaluated in a triethnic population from Galveston, Tex. Breast-feeding rates were 44.3% among Anglo-Americans, 13.5% among blacks, and 26.6% among Mexican-Americans. Mexican ethnicity, education levels among Anglo-Americans, and marital status were associated with the initiation of breast-feeding. Odds ratios for breast-feeding were 1.94 (95% confidence interval, 1.10 to 3.43) times higher in Mexican-American compared with black women, and 1.94 (95% confidence interval, 1.34 to 2.83) times higher in married than unmarried women. Anglo-American ethnicity and education, as main effects, were not significantly associated with breast-feeding, but their interaction was. Among Anglo-American women (in comparison with black women), the odds ratios of breast-feeding increased with education level, ranging from 1.84 for those with less than an eighth grade education to 7.46 for those with some college. In contrast to recent findings suggesting that education was more important than ethnicity in predicting breast-feeding, the odds of breast-feeding among Anglo-American compared with black women depended on the level of maternal education, but the odds of breast-feeding for Mexican-American vs black women did not depend on education.