In order to evaluate the persistency of the association between DDE and infant neurodevelopment we assessed mental and psychomotor development between 12 and 30 months of age in an ongoing cohort in Mexico. A total of 270 singleton children without perinatal asphyxia diagnosis, with a birth weight > or =2 kg, mothers>15 years of age with organochlorine maternal serum levels measured at least in one trimester of pregnancy, and who were evaluated at least in two of the four visits at 12, 18, 24 and 30 months of age, were included in this report. The Spanish version of Bayley Scales of Infant Development II (BSID_II; Bayley, 1993) was administered to the children and Psychomotor Development Index (PDI) and Mental Development Index (MDI) were calculated. Information about stimulation at home was measured using the Home Observation of Measurement of the Environment (HOME) at 6 months, and breastfeeding history was obtained through direct interviews with the mothers. Maternal serum DDE levels were determined during pregnancy by means of electron capture gas-liquid chromatography. The association between DDE prenatal exposure and neurodevelopment was estimated using separate generalized mixed effects models. Our results suggest that the association between prenatal DDE and infant neurodevelopment does not persist beyond 12 months of age even after adjusting for known risk factors for neurodevelopment. In addition, we observed an interaction between early home stimulation and mental improvement at 24 and 30 months of age (p<0.001). The association of DDE with infant neurodevelopment seems to be reversible. However, we cannot rule out that other DDT metabolites may play a role in neurodevelopment.