Ongoing surveys performed by Ross Laboratories demonstrate recent declines both in the initiation of breast-feeding and continued breast-feeding at 6 months of age. Comparing rates in 1984 and 1989, the initiation of breast-feeding declined approximately 13% (from 59.7% to 52.2%), and there was a 24% decline in the rate of breast-feeding at 6 months of age (from 23.8% to 18.1%). The decline in breast-feeding was seen across all groups studied but was greater in some groups than in others. Logistic regression analysis indicates that white ethnicity, some college education, increased maternal age, and having an infant of normal birth weight were all positively associated with the likelihood of both initiating breast-feeding and continuing to breast-feed to at least 6 months of age. Women who were black and who were younger, no more than high school educated, enrolled in the Women, Infants and Children supplemental food program, working outside the home, not living in the western states, and who had an infant of low birth weight were less likely either to initiate breast-feeding or to be nursing when their children were 6 months of age. The factors influencing the decline in breast-feeding were not uniform. There were fewer sociodemograpahic factors associated with the decline in the initiation of breast-feeding than in the decline in prolonged breast-feeding. While the disparity between older and younger mothers in initiating breast-feeding increased, there was an offsetting trend as the disparity associated with parity decreased. The only other significantly changed relationship for initiation of breast-feeding was that the disparity associated with higher income increased significantly: the decline in the rates of breast-feeding among the less affluent was greater than among the more affluent. Many more sociodemographic factors were significantly associated with declines in breast-feeding at 6 months of age. The disparity between those mothers not employed and those employed increased (from an odds ratio of 1.65 in 1984 to 2.43 in 1989). The disparities associated with age and parity both increased over time: the rate of breast-feeding declined more steeply among younger and primiparous mothers than among older and multiparous mothers. Similarly, the declines were greater among those enrolled in the Women, Infants and Children program (compared with those not enrolled), those with less than a college education (compared with some college education), and those not residing in the western region of the United States (compared with those residing in the West). Educational efforts to promote breast-feeding are needed for all pregnant women and should be particularly directed toward the groups who have experienced the most rapid recent decline in the rates of breast-feeding.