Among various organisms attacking skeleton weed,Chondrilla juncea, in Europe, a rust fungus,Puccinia chondrillina, and two powdery mildews,Erysiphe cichoracearumandLeveillula tauricaf. sp.chondrillaewere found to be the most damaging.P. chondrillinawas shown to be specific toChondrillaand has recently been introduced into Australia where skeleton weed is important in wheat cultivation. It has already spread throughout the weed infestations and is beginning to reduce plant populations. Encouraged by the result of theChondrillarust, the possible use ofPuccinia xanthiifor the control ofXanthium strumariumandX. spinosumhas also been studied. Current research on the possible use of phytopathogens in the biological control of some other weeds is reviewed.