A large-scale culture of hairy root of Ophiorrhiza pumila using a modified 3 l bioreactor was established. The hairy roots, incited by infection of Agrobacterium rhizogenes were grown in the bioreactor equipped with a stainless net. The final concentration of camptothecin was 0.0085% fresh wt of tissue, and the total production of camptothecin, an anti-neoplastic quinoline alkaloid, reached 22 mg over 8 weeks' culture in the reactor. Approx. 17% (3.6 mg) of the total camptothecin produced was excreted into the culture medium.