Abstract: A fragment of the ribosomal RNA gene of Schistosoma mansoni pSM889 and two DNA fragments specific to Echinococcus granulosus pHD5 and pEGlS have been used as DNA probes to assess the extent of genetic variability within E. granulosus. The DNA analysis,including restriction endonuclease digestion and Southern blot hybridization with the probes , did not demonstrate any genetic variation among E. granulosus collected from sheep in Xinjiang, Qinghai,Gansu and Ninxia. Similarly,there was no genetic variation among E. granulosus isolates collected from yak in Qinghai and Gansu provinces. The authors deemed that the yak isolates and the sheep isolates of E. granulosus appear to belong to a same strain.