Three rats were injected ip with a series of doses of N, N-dimethyltryptamine and tested in a self stimulation paradigm. Results indicated that higher doses of DMT (2.0 mg/kg and above) produced marked decrements in responding with lower doses having little or no effect. The data are discussed in terms of the drug's interaction with a tryptaminergic brain system that has been hypothesized to exercise inhibitory control over intracranial self stimulation.