2,3-Dialkyl(dimethylamino)indoles, synthesized via the Fisher indole synthesis, were found to weakly bind to 5HT1 and 5HT2 sites in brain cortical membranes (IC50 greater than 1 microM at both sites for all compounds). These (dimethylamino)indoles were relatively potent antagonists of the serotonin receptor in the rat stomach fundus. At higher concentrations, several of the compounds were weak agonists at this receptor. For direct comparison with data obtained in the isolated rat fundus, antagonism of serotonin-induced contractions at 5HT2 receptors in the rat jugular vein was also examined. Several of the compounds showed good selectivity for the fundus receptor relative to the 5HT2 receptor; together with minimal affinity for 5HT1 and 5HT2 binding sites in brain cortical membranes, these results support the idea that the serotonin receptor in the stomach fundus is distinct from 5HT1 and 5HT2 binding sites.