The transformed root culture of Polygonum tinctorium Lour. was established by infecting leaf explants with Agrobacterium rhizogenes A4. These cultures were examined for their growth and indigo content under various culture conditions. Among the four different culture media tested, SH medium showed the highest yield for root growth (28 mg dry wt/30 ml) and indigo production (152 mu g/dry wt). In SH medium, 30 g sucrose l(-1), 2500 mg KNO3 l(-1), 300 mg NH4H2PO4 l(-1) were the best conditions for indigo production at pH 5.7. The production of indigo in hairy roots slightly increased with the addition of 200 mg chitosan l(-1) (186 mu g/dry wt) and 20 U pectinase l(-1) (181 mu g/dry wt).