After a short description of the endocrine and nervous system and their similarities and differences, interactions between both parts are mainly dealt with in this brief review. This is especially exemplified by the modulation of receptors for neurotransmitters, of ion channels and other membrane components by neurosteroids and steroid hormones and the physiological significance of this regulation. Both classes of hormones can act via nongenomic and genomic actions. As biological responses to neurosteroids and steroid hormones in the nervous system exocytosis of peptide hormones and neurosteroids, regulation of neurotransmitter release, sexual brain development and male behavior and cell death are described. Neurotransmitters and their receptors are also modulated in their expression and biological activity by steroid hormones and neurosteroids in non-neuronal tissues, as demonstrated for GABA-receptors in the uterus and the embryonic cholinergic system. Because of the close links between endocrine and nervous system agents toxic for one component may also interfere with the other one.