Activity of soluble peroxidase and its isozyme patterns in carrot (Daucus carota L.)callus after excision and transfer to fresh Murashige and Skoog (MS)culture medium was investigated. The activity decreased markedly until day 1 and then increased gradually during days 7-10 at room temperature. The rapid initial decrease of the activity was also observed at low temperature (2°C)as well as in the presence of cycloheximide. However, the subsequent increase in the peroxidase activity after day I was slower at low temperature than at room temperature, and was not detected in the presence of cycloheximide. Activity of catalase decreased slightly within 4 days and cycloheximide enhanced the decrease of the activity. Two cationic and one anionic peroxidase isozymes disappeared or decreased markedly within the first day and one cationic and anionic peroxidase recovered 3-6 days after excision.