A series of N,N-dialkyltryptamines with methylthio or methylenedioxy substituents in the 4, 5, and 6 positions and methyl or isopropyl on the side-chain nitrogen has been synthesized. The behavioral pharmacology of these compounds showed them to possess Bovet-Gatti profiles characteristic of hallucinogens, and the 5-methylthio congener was the most potent. Binding studies at [3H]LSD and [3H]5-HT sites demonstrated that no single structural feature correlated with binding or behavioral changes and suggest a complex mode of action for these potential hallucinogenic agents.