Owing to its high proliferation and its ability of secondary metabolite production, hairy roots induced by infection of Agrobacterium rhizogenes to plants are expected to be a valuable culture system to produce useful secondary metabolites of plants. Hairy roots were induced by inoculation with A. rhizogenes on sterile seedlings of Hyoscyamus niger. Hyoscyamine (1) as the main tropan alkaloid was isolated in high yield, together with scopolamine (2), 7β-hydroxyhyo-scyamine (3) and 6β-hydroxyhyoscyamine (4) from the hairy roots of H. niger. The highest content (2.7% dry weight) of 1 was observed in MS liquid medium. In the course of our study on the alkaloid production, it was shown that the hairy roots of H. niger gave phytoalexins, lubimin (5) and solavetivone (6), by treatment with Cu^<2+>. The hairy roots of H. albus also gave 1 and 2 by treatment with Cu^<2+>. The hairy roots of H. albus gave seven phytoalexins, 5-11, by treatment with methyl jasmonate (JAMe). The Structures of four new phytoalexins, 8-11, were determined to be (3R,4S,5R,9R)-3-hydroxy-9-tigloyloxysolavetivone, (3R,4S,5R,7S,9R)-3-hydroxy-9-(3-methyl-2-butenoyloxy)solavetivone, (3R,4S,5R,7S,9R)-3-hydroxy-9-isobutanoyloxysolavetivone and (3R,4S,5R,7S,9R)-3,9-dihydroxysolavetivone by mean of spectral methods. The induction pattern of phytoalexins by treatment with JAMe was different with those treated with Cu^<2+>. Co-treatment of the hairy roots with JAMe and Cu^<2+> gave only 2 in several time higher yield than the treatment with JAMe.