The scope of the plenary lecture at the occasion of the Xth Meeting on Heterocyclic Structures in Medicinal Chemistry, Palermo 2002, is considerably larger than that of the main lecture at the XVIth International Symposium on Medicinal Chemistry, Bologna 2000, described by Froestl et al. in Farmaco 56 (2001) 101. Additional information is presented, in particular, on the reaction conditions for the 31 step synthesis of the combined affinity chromatography and photoaffinity radioligand [125I]CGP84963 and on the recent developments of the molecular biology of GABA(B) receptors.