Carrot hairy roots have shown vigorous growth and extensive lateral root branching in the absence of phytohormone. The production of peroxidase which was not detected in suspension cells was observed in high amounts in carrot hairy root. High peroxidase activity (19.2 Ug(-1) fresh cell weight) was obtained by increasing the total phenolics concentration in the media. Peroxidase synthesis could be increased using elicitors such as yeast extract, V2O5, and Hg2Cl2, which are known to induce the synthesis of PAL (phenylalanine ammonia lyase). As the initial sucrose concentration in the medium increased, peroxidase activity and total phenolics increased while final cell mass decreased. A high level of sucrose also affected the elevation of the phenolics concentration in the cell. By adopting a two-stage culture method, the activity of peroxidase (55 U g(-1) fresh cell weight) was ten times higher than that of a single-stage culture (5 U g(-1) fresh cell weight) and about three times higher than that of field-grown horseradish on an activity per weight basis.