Abstract: Chromtin bound DNA-dependent RNA polymerase was isolated from mung bean cotyledon segment during dedifferentiation. The results show that the activity of RNA polymerase in dedifferentiation tissue after culturing for 3 days is higher than that of 5 and 7 days. The activities of RNA polymerase in dedifferentiation tissue for 3, 5 and 7 days are higher than that of control. After fractionation on DEAE-CELLUOSE column, three enzyme peaks were detected in the elute fractions. According to their sensitivity to a-amanitin they are the RNA polymerases I, II and III resp.