In this second special issue on signal transductionleading specialists in their fields again present overviewsof topics related to the highly topicalsubject of signaltransduction. The first contribution, by Keppler, deals withthe biosynthesis, transport, inactivation, and analysis ofleukotrienes. Mohr et al. present an excellent overview ofthe biology of the peptide hormone oxytocin and its role insignal transduction.The review by Holzer describes thesignificance of peptinergic sensory neurons in the controlof vascular functions. In the contribution by Wolf etalthe molecular biology of the Y chromosome is discussed.