The influence of maternal smoking the nutrient content of breastmilk and impact on infant longitudinal growth rate is unknown. From birth, 23 smoking (S), (7.1 +/- 4.4 cigarettes/day) and 23 non-smoking (NS) mother-infant pairs were followed. The breastmilk volume by deuterium dilution, zinc (Zn), copper (Cu), and iron (Fe) in breastmilk and hair by atomic absorption (AAS) and cotinine levels by radio-immuno-analysis (RIA) were evaluated. Birthweight was similar in contrast to height, and infants grew normally. Height and height-for-age (ZHA) were significantly lower in S infants and weight-for-height (ZWH) was higher in S infants in the third month, caused by slower height growth. Cotinine was 19 times greater in the S mothers and six times higher in their infants, as compared to NS group. Breastmilk volume was 743 +/- 119 g/day (S) and 742 +/- 111 g/day (NS), with no difference in zinc, copper, iron contents, except for cadmium (Cd). In infant's hair, all minerals were higher in the S group. Smoking affected infant's height during breastfeeding, attributed to an eventual impaired bioavailability of essential nutrients.