L-DOPA (3,4-dihydroxyphenylalanine) production by Stizolobium hassjoo cells was investigated. After inducing an authentic callus, a potent cell line named Sh-2 was bred. The cell line was acclimated by repeated subcultures. The favorable conditions for obtaining high productivity of L-DOPA were found to be the precise control of pH, adequate IAA (indole-3-acetic acid) concentration and color of cells which reflect melanin production. By referring to the assumption that the prosthetic group of the phenol oxidase is copper and that the catalytic activity of the enzyme is based on the change of the valency of cupric ions, Cu++ concentration in culture medium was increased. When Cu++ concentration in basal Murashige-Skoog (MS) medium was increased 25-fold (0.625 mg/l of CuSO4 . 5H(2)O), the total L-DOPA content in the culture medium was about twofold that obtained in basal MS medium. A similar effect was confirmed with Co++. Another strategy used in this work was to lower the ionic strength in the culture medium so that inhibition of the cell growth can be reduced. Dilution of the MS medium influenced the L-DOPA content in the cells. A 1/3 dilution of MS medium supplemented with optimized concentrations of constituents determined from this investigation resulted in the 2.05-fold increase in L-DOPA content.