Milk samples from 33 women from a rural area of the Ivory Coast were analyzed once a month. In two longitudinal studies covering 23 months of breast feeding, analyses of lipid components and protein were performed. The compositions remained virtually constant over 23 months of lactation except for a decrease of protein concentration during the first 6 months, a rising trend of myristic acid (14:0) and a falling trend of oleic acid (18:1). Infants were growing well on breast milk with nothing else for the first 5 months, but thereafter their growth curves were no longer satisfactory as judged by Western standards: weight for age (percentage of Harvard standards) decreased from 5 to 10 months of age to level off thereafter at a value of 80%. The mothers' weight for height remained constant. In a cross-sectional study, additional determinations were performed: aminograms, lactose, calories, iron, copper, manganese, zinc, and vitamin E. All data were compared with those of the literature. Lauric (12:0) and myristic (14:0) acids were higher, total lipids and polyunsaturated fatty acids lower than those published for Western countries. Plasma composition of the mothers showed lower levels of albumin, lipids, and polyunsaturated fatty acids as well as blood hemoglobin. Possible correlations between various variables such as milk composition, plasma levels, and anthropometry were calculated and discussed.