Analysis of the 1973 National Survey of Family Growth shows a continued downward trend in breast feeding by successive cohorts of American mothers. The downward trend is evident in both measures of incidence (ever-breast feeding) and duration of breast feeding for first and higher-order births. For all cohorts higher-order births are less likely to be breast fed than first births. However, breast feeding of higher-order births is typically of a longer duration. Differentials in breast feeding reveal strong associations with indicators of social class; women who are college graduates, who work as professionals, and who are married to professional husbands are most likely to breast-feed their infants. Differentials in average duration of breast feeding are often reversed from differentials in ever-breast feeding.