Dietary survey in lactating mothers and analysis of composition of breast milk were performed. 73 healthy women, full term and normal delivery, 21-32 years of age, without family history of "insufficient milk secretion" or environmental, psychiatric and emotional disturbance were included in this study. 33 of them were female workers in the urban district and 40 of them were peasant women in the countryside. By comparing the daily dietary nutrient intakes of the urban and rural groups of lactating mothers with that recommended by the Chinese Nutrition Society (1981 revised), one can see that except iron and thiamine, all the others were below the standard recommended. Among these, total calories were only 82.7% and 77.3% respectively, protein 80.6% and 73.1%, riboflavin 96.7% and 41.1%, calcium 21.9% and 25.2% respectively. Intake of animal protein, total fat and fat energy ratio of the urban group were higher than that of the rural group, meanwhile the content of protein, fat and zinc in the breast milk of the urban group were also higher than that of the rural group, By stepwise regression analysis the following regression function was conducted;Y = 0.9-107 + 0.007x, Y represent the estimated protein content in the breast milk, and x, the fat energy ratio in the mothers diet. Positive correlation was seen between the dietary intake of animal protein and zinc content in the breast milk. r=0.47, p