Knowing early nutritional status have been shown to be an important factor in determining the activity level of rats later in life, we studied offspring of dams which had received 50, 70 or 700 mg/kg of 2,4-Dichlorophenoxyacetic acid (2,4-D) during nursing. Neonatal tissues and the stomach content (milk) were examined up to 16 post natal days to detect body and organs weight alterations and 2,4-D residues after 2,4-D maternal dosing every-other-day, from post natal day 1. We detected 2,4-D residues in stomach content, blood, brain and kidney of 4-day-old neonates breast-fed by 2,4-D exposed mothers and onward. 2,4-D residues were dose- and exposure-time-dependent. The highest dose impaired body growth, as well as low tissue weights and diminished stomach contents. Levels of 2,4-D residues in stomach content, blood, kidney and brain of post natal rats (age PD 4-PD 16) fed through lactation from dams treated with 2,4-D demonstrated that 2,4-D was transferred to the neonates and the diminished body and tissues weight during this developmental period could be due to a diminished milk intake or/and to the direct 2,4-D toxic effect. Besides, when the herbicide treatment (100 mg 2,4-D/kg) was withdrawn from the dams, 2,4-D residues remained in the stomach content of neonates for at least one week. This fact indicated that dams continued depurating the herbicide through their milk.