1. Hydrogen sulphide (H2S) is a broad spectrum toxicant that occurs widely in nature and is also released by a variety of industrial activities and processes. 2. The central nervous system (CNS) appears to be the major target organ. 3. There is great potential for insult or injury to the developing or immature CNS. 4. The risk of chronic or repeated exposures to low concentrations have not been well defined. 5. Exposure to low concentrations of H2S to time-pregnant rats from day 5 postcoitus until day 21 postnatal results in architectural modification of cerebellar Purkinje cells, alteration of putative amino acid neurotransmitters and changes in monoamine levels in the developing rat brain up to day 21 postnatal. 6. H2S-induced alterations in monoamine tissue levels observed in the developing rat brain return to control values if exposure is discontinued during development, that is, at day 21 postnatal.