OBJECTIVES: To investigate a possible lasting impact of dichlorodiphenyl trichloroethane (DDT) exposure in neonatal life on mental capacities in later life. MATERIAL AND METHODS: Relationships were evaluated by correlation and regression analysis between total DDT concentrations in human breast milk in the years of birth (1984/1985) and measurements of mental capacities obtained in pupils of the PISA 2000 studies as well as percentages of backward children in Germany in 1994/95. RESULTS: Comparing total DDT levels in human milk during the years of birth (1984/85) evaluable for eleven PISA countries with assessed mental capacities of 15-year-old pupils of PISA International, a signifi cant inverse correlation was found (p < 0.001), even after adjustment for socioeconomic statuses (p = 0.001). Furthermore, a signifi cant inverse correlation (p < 0.001) was also obtained between the total DDT concentrations in human milk in 1984/85 in ten foreign countries of three continents plus fourteen Federal States of Germany and the mental capacities of 15 year-old pupils of PISA International plus PISA National (Germany) 2000. Finally, a signifi cant positive correlation was observed between total DDT contents in human milk in 1984/85 and the percentages of backward school children in 1994/95 in Federal States of Germany (p < 0.001). CONCLUSIONS: These data – in association with additional experimental and epidemiological fi ndings – suggest that DDT is a “neuroendocrine disrupter” as well as a “functional teratogen” leading to harmful effects on brain development and mental capacities in later life. Thus, a neuroendocrine prophylaxis during critical developmental periods in early life – as recommended by our group since many years – appears to be most important for primary preventive medicine but even for “preventive pedagogics”. The validity of these theses should be retested in future PISA studies.