The synthesis, brological activity and electrostatic propertres of the thiadiazolyl-tryptarnine (2), a novel 5HTf D rece-ptor agonist, are described The compound was synthesised in four steps from the readily available tryptamine ester (7~) and it was found to be remarkably more potent than the corresponding oxadiazole analogue (l), both in functiinal and binding assays