Harmine, Win-2299, and Nalline in single dosage produce many new mental effects in schizophrenics grossly similar to those elicited by mescaline and LSD. Many of the same effects are reported in normals after harmine and Nalline (other workers). unlike mescaline and LSD at usual dosage levels, the present psychotomimetics regularly produce drowsiness and sleep along with the aberrant mental effects. The resultant state is partly that of "hypnagogic" visual hallucinations or imagery. The results with increased dosage suggest that the basic effect of these agents is to produce an acute toxic reaction type. The difference between them and mescaline or LSD with respect to clouding of consciousness and certain aspects of the hallucinogenic response may be quantitative rather than qualitative. The indole nucleus is not necessary in the structure of psychotomimetics since Win-2299 and Nalline are non-indoles. The tertiary nitrogen grouping may contribute to certain aspects of psychotomimetic action.