OBJECTIVE: To induce hairy roots of Gynostemm apentaphyllum by Agrobacterium rhizogenes strains. METHODS: Hairy roots were induced by the co-culture method of explants and Agrobacterium rhizogenes strains. Effects of different Agrobacterium rhizogenes strains, explants, pre(co)-culture time, Bacterial concentration, infecting time, As concentration and antibiotic medium on the transformation frequency were studied. RESULTS: The highest induction frequency was obtained form leaf 2 days co-cultivation, which were induced by Agrobacterium rhizogenes OD 600 0. 8 for 10 min, 100 micromol/L As and MS + 300 mg/L Cab. CONCLUSION: Hairy roots were induced by co-cultivation and the optimum induced condition were determined.