Abstract: Tetrandrine is a new antisilicosis drug used in this country. We have studied further its biotransformationAs standards, two tetrandrine-N-2'-oxide epimers and N-2'-nor-tetrandrine were prepared, one of the two oxide epimers is a new compound. Its structure was elucidated on the basis of chemical and spectral data (NMR, MS). The metabolites of tetrandrine in liver, lung and urine of rats and in urine of patients after oral administration of tetrandrine were compared with the standards by TLC and HPLC. The results showed that, in addition to tetrandrine itself, the above-mentioned metabolic products of tetrandrine were probably present in the organs and in urine. The content of tetrandrine-N-2'-oxide was about 9% of that of tetrandrine in rat liver, while the content of N-2'-nor-tetrandrine was about 7%.In this paper, the experimental conditions of GC and HPLC for tetrandrine were reported.