Abstract: Shikonin is one of the active components isolated from the dry root of Arnebiaeuchrona(Royle) Johnst(AERJ).It has been shown to have anti inflammatory activity on formalde-hyde induced paw swellil1g in rats.Preparations of AERJ has been used clinically in curing phlebitisand vascular purpura,In the present study ,sc administered shikonin was shown to have significantinhibitory effects on ear edema induced by croton oil in mice and paw swelling induced by yeast inrats.In order to investigate the influence of shikonin on biosynthesis of LTB4 and 5-HETE, an in vitro leukocyte incubation svstem was adopted.The results showed that shikonin has fairly strong inhibitoryeffects on LTB₄ and 5-HETE biosynthesis.Its effects and concentrations fit a positive relationshipwithin the range of 10^-7～10^-4mol·L^-1.The equations of inhibition(Y)versus concentration(X,LogC)obtained by linear regression were Y= 166+18. 7X(r=0. 9319) for LTB₄ and Y= 173+18.7X(r=0.9856)for 5-HETE. The IC₅₀ were 6.2× 10^-7 and 2.6×10^-7mol·L^-1,respec-tively.The results also indicate that natural shikonin derivatives have similar inhibitory effects on LTB₄ biosynthesis. These results suggest that inhibition of LTB4 and 5-HETE may play a major role inthe mechanism of anti inflammatorv effects of shikonin。