The identification of N:N-dimethyltryptamine in urine samples of drug-free chronic schizophrenic patients is confirmed by gas chromatography-mass spectrometry of both the free tertiary amine and the trimethylsilyl derivative. A quantitative method using single ion detection (m/c 58) is described. Urine samples from the six subjects were positive for bufotenin by both thin-layer chromatography and gas chromatography-mass spectrometry. Samples from three of the six subjects were also positive for N:N-dimethyltryptamine by both methods. Comparable results obtained by thin-layer chromatography and by single ion detection during gas chromatography-mass spectrometry showed that the levels of N:N-dimethyltryptamine in 24-hr urine samples were less than 1 microg.