AbstractNuclear organizer Region (NORs) are parts of the nucleoli involved in the synthesis of ribosomes. Silverstainable proteins of the nucleolar organizer regions (AgNORs), which are increased in neoplastic cells, can be localized in tissues embedded in resins. The method was adapted to bone, which needs to be processed undecalcified for histomorphometric purposes. Sections of undecalcified biopsies embedded in methacrylic resins were extensively demineralized in EDTA. They were stained for AgNORs and conterstained with metanil yellow. Sections were flattened with polyvinyl alcohol (a hydrophilic glue), which makes them suitable for light microscopy. The same method was applied for transmission electron microscopy (TEM) by embedding undecalcified blocks in an hydrophilic resin (LR-White). Ultrathin sections of bone mounted on gold grids could be stained for AgNORs after EDTA demineralization. The interest of hydrophilic resins as embedding media was evidenced for AgNORs staining. (The J Histotechnol19:27, 1996)