The location of rRNA processing was analyzed by using in situ hybridization with ITS1 probe and immunolabeling of anti-fibrillarin mAb in pea (Pisum sativum) root pole cells. The results showed that rRNA processing sites were in dense fibrillar components (DFCs) and granular com-ponents (GCs), but not in fibrillar centers (FCs). Low doses of actinomycin D (AMD) treatment can selectively suppress pre-rRNA synthesis but cannot disturb the processing of preformed pre-rRNAs. With AMD treatment prolonged, the density of labeled signals gradually decreased, indicating the preformed pre-rRNAs were gradually processed. The location of rRNA processing was analyzed by using in situ hybridization with ITS1 probe and immunolabeling of anti-fibrillarin mAb in pea (Pisum sativum) root pole cells. The results showed that rRNA processing sites were in dense fibrillar components (DFCs) and granular com -ponents (GCs), but not in fibrillar centers (FCs). Low doses of actinomycin D (AMD) treatment can selectively suppress pre-rRNA synthesis but can not disturb the processing of preformed pre-rRNAs. With AMD treatment prolonged, the density of labeled signals gradually decreased, indicating the preformed pre-rRNAs were gradually processed.