CGS 12066B is an agonist of the serotonin (5-HT) receptor subtype 5-HT (IC = 51 nM). It is selective for 5-HT over 5-HT and 5-HT receptors (ICs = 876 and 6,480 nM, respectively), as well as α-, α-, and β-adrenergic, and dopamine D and D receptors (ICs = >6,000, >1,000, >1,000, >5,000, and >5,000 nM, respectively). CGS 12066B inhibits forskolin-induced cAMP accumulation in opossum kidney cells when used at concentrations ranging from 0.001 to 1 µM. In vivo, CGS 12066B reduces 5-hydroxy-L-tryptophan (5-HTP) accumulation in the fronto-parietal cortex (ED = 7.92 µmol/kg) and induces dorsal raphe cell firing in rats (ED = 358 nmol/kg). It decreases interfemale and intermale aggression in Syrian hamsters.