Adventitious roots were induced from 2-year-old, hyoscyamine rich suspension cultures of Hyoscyamus niger L. The cultured roots grew well in Linsmaier-Skoog medium containing 10 (-8)M 6-benzyladenine with 3% sucrose and produced much more scopolamine (0.12-0.30% dW) than hyoscyamine (0.04-0.08% dW). The alkaloids were detected in the medium as well as in the cells. Ten to twenty percent of the hyoscyamine added to the medium was converted to scopolamine within 24 days by the root cultures, but only 1 to 3% was converted by the suspension cultures. Scarcely any of the scopolamine added to the medium was converted to hyoscyamine by either culture.