Very recently, after a long-lasting, worldwide moratorium on research of hallucinogenic agents, a good number of advanced countries have been revising their position, and start to approve testing the physiological and therapeutic effects of hallucinogens in human subjects. The purpose of this article is to review safety information available in the literature on hallucinogen use, and sort out those data from the reported complications of their abuse. Because of prohibitory regulations of the last 35 years, there are difficulties in achieving this kind of evaluation. Our approach has to be broad, and at times retrospective, in contrast to the well-controlled, focused, prospective design of the premarketing trials of legal drugs. The article summarizes the analyses in anticipation of supportive regulatory changes for the use of hallucinogens in well controlled studies and strictly supervised clinical trials.