In this second special issue on signal transduction leading specialists in their fields again present overviews of topics related to the highly topicalsubject of signal transduction. The first contribution, by Keppler, deals with the biosynthesis, transport, inactivation, and analysis of leukotrienes. Mohr et al. present an excellent overview of the biology of the peptide hormone oxyin and its role in signal transduction.The review by Holzer describes the significance of peptinergic sensory neurons in the control of vascular functions. In the contribution by Wolf etal the molecular biology of the Y chromosome is discussed.