This study presents results of surveys conducted on a continuous basis over a period of years to determine the trend in the incidence of breast-feeding. Questionnaires were mailed to large samples of mothers, representative of the national distribution of births, asking them what type of milk they fed their infants over a period of time. Demographic characteristics of mothers who breast-fed were also obtained. From 1955 to 1971, there was a progressive decline in breast-feeding, followed by a resurgence of its incidence through 1979. Not only are more mothers breast-feeding, more are continuing to do so for a longer period of time throughout the months of their infants' most rapid growth and high nutritional requirements. It is also apparent that the increased incidence of breast-feeding has not been limited to higher income, better educated mothers.