Transformations of potato (Solanum tuberosum cv. Yayla kizi) and tobacco (Nicotiana tabacum cv. Samsun NN) were achieved using tuber discs and internodes via Agrobacterium rhizogenes 8196 wild strain on MS (11) media supplemented with 5 mu M naphthalene Acetic Acid (NAA). In this study, we examined the effects of Naa on hairy root formation of potato and tobacco. Cultures of bacteria were concentrated at O.D. (600)=0.2 for inoculation and MS media supplemented with 1 mu M Cefotaxime (Cx) and 5 mu M NAA were used for co-cultivation. Transformed hairy roots were obtained after three weeks in a regulated plant growth cabinet at 25 degrees C with 16 hours light followed by 8 hours dark period. DNA was extracted from these roots and digested using EcoR I and Hind III restriction endonucleases, and transformation was confirmed using the Southern blot hybridization method with [gamma(32)P] CTP labeled Ri plasmid DNA of A. rhizogenes 8196.