In the early 1980's, the dispute on the existence of a multiplicity of receptors for neurotransmitter was at its height. Several subtypes of serotonin (5-HT) receptors were proposed on the basis of radioligand binding assays. In order to provide further support to the existence of these receptors we performed quantitative autoradiographic mapping of the binding of several ligands for the 5-HT1 receptor labeling the subtypes 5-HT1A, 5-HT1B and 5-HT1C, and characterized pharmacologically these different receptors. The results demonstrated differential localization of the subtypes of 5-HT1 receptors indicating that they were expressed by different cell populations, probably neurons, in the brain and further supporting their reality. Shortly afterwards, the cloning of the genes coding for these 5-HT receptors, and many others, ended the dispute by demonstrating that they were different proteins. The advent of Molecular Biology provided new methodologies for the study of the chemical and molecular anatomy of 5-HT receptors in brain, by visualizing cells expressing their mRNA by in situ hybridization and showed that the family of mammalian 5-HT receptors has 14 members, a figure much larger than ever suspected at that time. This article is part of a Special Issue entitled SI:50th Anniversary Issue. (C) 2016 Elsevier B.V. All rights reserved.