Abstract: A new diterpene triepoxide, 16-hydroxytriptolide was isolated from the root and loves of Tripterygium wilfordii Hook.f. 16-Hydroxytriptolide was obtained as white cluster crystal, mp 232～233.5℃. Its molecular formula is C₂₀H₂₄O₇. The structure and stereochemistry of 16-hydroxytriptolide was established as L₂ (Fig. 1 )on the basis of spectral data (IR, MS, UV, ¹H-NMR, ¹³C-NMR, 2d-NMR, NOE) and X-ray crystallographic analysis. In the pharmacologic screening, 16-hydroxytriptolide showed definite antiinflammatory actions and strong immunosuppressive and antifertile activities. In antiinflammatory action, its half effective dose (ED₅₀) was 0.12mg/kg with the model of croton oil induced ear swelling of mice. In immunosuppressive action, its ED₅₀ was 0.05mg/kg with the model of the formation of haemolysinantibody of mice. Its lowest effective dose (po) was 0.027mg/kg×33d in antifertile action.