The study will investigate sex steroid-regulated gene expression in two sexually dimorphic brain regions i.e. the preoptic region, the bed nucleus of stria terminalis and the ventromedial hypothalamic nucleus, which are part of the neural network controlling sexually dimorphic behaviours and gonadal dysfunction, but differ in developmental profile and nuclear steroid receptor distribution. Effects at the central level of neuroendocrine control in males and females will be compared with effects on gene expression in reproductive organs (uterus, prostate). Effects of acute administration and long term developmental exposure to chemicals will be studied. The study is expected to provide information on working mechanisms of endocrine active chemicals on sexual brain differentiation and development of reproductive organs, to identify useful biological/biochemical parameters that could be used for screening purposes. Possible effects in brain development may be of specific relevance for children as a susceptible sub-group.