Abstract
A Δ9 -THC metabolite has been identified in human urine as an ester linked glucuronide of Δ9 -THC-11-oic acid. Its identity was established by a comparison of mass spectra from the metabolite extracted from human urine and synthetically prepared material. Δ9 -THC-11-oic acid glucuronide was found to be responsible for the major part of RIA crossreactivity in urine with the Guildhay cannabinoid antiserum used in this study.