Preparations of the plant Acorus calamus (calamus or sweet flag) (A. calamus) are available via internet trade and marketed as being hallucinogenic. In 2003-2006, the Swedish Poisons Information Centre received inquiries about 30 clinical cases of intentional intoxication with A. calamus products. The present investigation aimed to identify alpha- and beta-asarone, considered active components of A. calamus, and metabolites thereof in urine samples collected in seven of these cases. To further aid the identification of asarone biotransformation products, a calamus oil preparation was incubated with the fungus Cunninghamella elegans, which is used as a microbial model of mammalian drug metabolism. Using gas chromatography-mass spectrometry (GC-MS) analysis in selected ion monitoring mode, alpha-asarone was detected in five urine samples at concentrations ranging between approximately 11 and 1150 microg/L and beta-asarone in four of those at approximately 22-220 microg/L. A previously identified asarone metabolite, trans-2,4,5-trimethoxycinnamic acid (trans-TMC), was detected in the fungus broth by liquid chromatography-tandem mass spectrometry whereas cis-TMC was tentatively identified in the human urine samples. Using GC-MS, a hydroxylated asarone metabolite was identified both in fungus broth and urine samples. However, this study demonstrated no evidence for the presence of 2,4,5-trimethoxyamphetamine, claimed as a hallucinogenic component of A. calamus. The main clinical symptom reported by the patients was prolonged vomiting that sometimes lasted more than 15 h.