We describe a new staining technique (H-Ag-S) which allows observation and counting ofactive nudeolus organizer regions (NORs) and evaluation of the amount of DNA in the same cell nudeus. The procedure consists of combining a modified AgNOR staining method with the Feulgen reacnon. A sequential procedure is proposed, based on the determination ofoptimal staining conditions. The technique, Clavaguera A, Querol E, Coll D, GenescaJ, EgozcueJ (1983): Cytochemical studies on the nature ofNOR (nucleolus organizer region) silver stainability.