The psychotomimetic agent dimethyltryptamine (DMT) has been identified as an endogenous compound in the central nervous system of rodents using a sensitive electron capture gas chromatographic technique. DMT along with its proposed precursor, tryptamine, were identified and quantitated as the heptafluorobutyryl derivatives. A specific high affinity binding site on synaptosomal membranes has been proposed for DMT. This proposal is based on equilibrium dialysis experiments which indicate that DMT at a concentration of 1 x 10-5 M will displace d-LSD on isolated membranes but will not displace bound serotonin at the same concentration. When DMT interacts with the synaptosomal membranes at a concentration of 5 x 10-10 M, the membrane-bound enzyme adenylate cyclase is stimulated such that adenosine 3’,5’-monophosphate (CAMP) is produced at a rate of 100 pmole/min/mg of protein (2.3 times the endogenous rate). It has also been shown that its presumed precursor, tryptamine. inhibits this process. LSD appears to exhibit a high affinity for the proposed DMT binding site but seems to have a low intrinsic activity. From data obtained in this study it has been postulated that DMT may have in vivo activity similar to those proposed neuroregulatory agents. These data further of action of d-LSD may be the displacement on the neuron.