Fifteen species of weedy plants were collected from potato fields between July and September 2006 In Erzurum (Turkey). In total, 21 isolates of Verticillium dahliae were obtained from Cirsium arvense, Convolvulus arvensis, Chenopodium album, Polygonum lapathifolium and Sinapis arvensis. Of these, 15 were isolated from C arvense, and one or two isolates from the other weed species. This is the first report of V dahliae isolated from these weed species ill Turkey. All isolates from weeds were assigned to vegetative compatibility groups (VCGs) using nitrate-nonutilizing (nit) Mutants. Two VCGs were found and identified as VCG 2B (11 isolates) and VCG 4A (10 isolates) by using tester isolates of known VCGs. Pathogen 1 city of V dahliae isolates was tested oil potato by the root-dip method. Both VCG 2B and VCG 4A isolates from weeds were pathogenic to potato.