The relationship between the brain and the endocrine system is now seen to extend far beyond the regulation of somatic hormone production by the hypothalamus and pituitary: the brain itself can be considered both as an endocrine organ, producing hormones that act both within and outside the central nervous system, and as a target for hormones. The current extent of this concept with respect to the gonadal hormones was explored at a recent meeting (‘Hormones and the Brain’, Third Endocrinology Colloquium of the Fondation Ipsen, Paris, December 8, 2003). The discussion, reviewed in this article, ranged from intracellular signalling pathways and intercellular networks regulating hormone production and action in the central nervous system to hormone involvement in the generation of sexual behaviour and in development, plasticity, neuroprotection and repair. The hormonal contribution to psychiatric and neurodegenerative illnesses was also examined. The picture presented is complex, with layers of controls and with hormones that have diverse actions at different sites in the central nervous system. This richness of actions and functions is providing some interesting leads for developing new therapeutics.