Human Liver microsomal oxidation products of Δ⁸-tetrahydrocannabinol (THC) were isolated and identified by thin-layer chromatography, gas chromatography and gas chromatography-mass spectrometry. As the results, five monohydroxylated metabolites including 11-hydroxy-Δ⁸-THC, and 8β, 9α-dihydroxyhexahydrocannabinol were identified as trimethyl-silyl derivatives. Isolation of the dihydroxylated metabolite suggests that epoxy metabolite (s) may be formed from Δ⁸-THC in humans.