One hundred eleven isolates of Verticillium dahliae were obtained from potato plants in Erzurum province, Turkey. The pathogen was isolated from 7.6% of the stems collected. All isolates were assigned to vegetative compatibility groups (VCGs) using nitrate-nonutilizing (nit) mutants. In total, 240 nit mutants were obtained from V. dahliae isolates, and classified as nit1 (71%) and nitM (29%). Two VCGs were found and identified as VCG 2B (34 isolates) and VCG 4B (77 isolates) by using tester isolates of known VCGs. Pathogenicity of V. dahliae isolates was tested on potato (cv. Marfona) by the root-dip method. Both VCG 2B and VCG 4B isolates showed similar aggressiveness on potato. This is the first study of VCGs of V. dahliae isolates from potato plants in Turkey.