Exposure to insecticides is ubiquitous in the developing world, where women who perform farming activities throughout pregnancy are routinely exposed.  Although several birth cohort studies in the U.S. have shown persistent neurodevelopmental effects of prenatal organophosphate (OP) insecticide exposure, the neurodevelopmental pathways and timing of exposure leading to adverse outcomes is not clear.  Thus, regulatory agencies have not altered risk assessment standards nor recommended reductions in exposures to pregnant women.  The proposed longitudinal birth cohort study in Thailand will: 1) build capacity of Thai researchers to develop innovative and competitive studies of pesticide related neurotoxicity 2) measure metabolites of OP and pyrethroid (PYR) insecticides during each trimester of pregnancy, and 3)evaluate the impact of prenatal OP and PYR insecticide exposure on neurodevelopmental trajectories from birth to age 3.   In collaboration with Chulalongkorn University (CU) in central Thailand and Chiang Mai University (CMU) in northern Thailand, 300 pregnant women will be recruited.  Eight serial urine samples, 4 serial blood samples, and umbilical cord blood will be collected during pregnancy to document temporally-resolved insecticide exposure during each trimester.  The Brazelton Neurobehavioral Assessment Scale will be administered to offspring at birth followed by tests of visual attention, regulation of emotion, memory and inhibitory control to determine how the “cascade” of neurologic development ultimately affects overall cognitive function (e.g., Bayley-III).  Capacity building activities include development of core analytic laboratory facilities at CMU and neurodevelopmental facilities at CU along with courses to promote grant writing and international scientific publications.