Forty-five fungal isolates were obtained from sclerotia of Rhizoctonia solani on potato tubers in Erzurum, Turkey. The interaction between fungal isolates and R. solani was studied in dual culture technique. Some fungal isolates affected R. solani by antibiosis and/or parasitism. Results of the antagonism tests showed that Acremonium sp., Gliocladium viride, Paecilomyces marquandii, Paecilomyces sulphurellus, Penicillium camemberti, Penicillium expansum, Penicillium frequentans (ME-50), Penicillium nigricans, Penicillium olsonii, Penicillium phialosporum, Sporothrix sp. (MCY-4), Sporothrix schenckii, and Verticillium dahliae isolates produced an inhibition zone in front of the R. solani colony to a varying degree. Trichoderma harzianum isolates were able to overgrow the mycelium of R. solani. Physical colony contact was observed between the remaining 21 fungal isolates and R. solani. Furthermore, coiling of hyphae of Acremonium sp., Acremonium strictum, Gliocladium catenulatum, G. viride, and T. harzianum around those of R. solani was commonly observed.