Abstract: Yungumycin,produced by a Streptomyces strain which was isolated from a soilsample collected in Guanping Nature Conservation Zone, Yunnan Province, China,has been verifiedto be identical with gougerotin,Determined by clonogenic assay,the IC₅₀ of yungumycin to KB cellswas found to be 1 μg·ml^-1.By spermatogonial asSay,the activity of yungumycin was very close tothat of 5-FU and MTX, Administered by ip route,yungumycin showed moderate inhibition againstcolon carcinoma 26 in mice, However,yungumycin by oral administration exerted highly inhibitoryeffects on both colon carcinoma 26 and sarcoma 180(solid tumor)in mice and the inhibition ratesreached 85%and 83%, respectively, at tolerable dose,Compared at equitoxic dose of 1/6 LD₅₀,theinhibitory effect of yungumycin(15 mg· kg^-1)on sarcoma 180 was similar to that of 5-FU ( 40mg· kg^-1),showing 72%and 70%tumor inhibition,respectively.Initially, gougerotin wasreported as an antihacterial antibiotic without mentioning its antitumor activity.The present studiesdemonstrate that yungumycin(gougerotin), by oral administration,may be useful in cancerchemotherapy.