Little, however, is known regarding statistically significant differences in activity among substituted tryptamines . It has been claimed that 6-hydroxyN :N-dimethyltryptamine is more potent than DMT (15) : however, general agreement on this point has not been forthcoming (16,17) . In this paper we report on statistically significant differences in activity, as characterized by the ability to disrupt the conditioned avoidance response of trained rats, among a number of naturally occurring and synthetic tryptamines .