A survey is given of methods involving decalcification and paraffin embedding of iliac crest biopsy for osteological and haematological diagnostic procedures. In order to avoid shrinkage, loss of antigens, and fading of ferritin iron and enzymes, a fixative has been designed that is composed of an aqueous solution of calcium acetate (10(-1) M), glutaraldehyde (0.5%), and formaldehyde (1%; CGF). CGF-fixated specimens are decalcified in an aqueous solution of 10% di-sodium ethylene-diaminotetraacetate (EDTA) neutralized by tris[hydroxy]methylaminomethane and embedded in paraffin. Tissue prepared in this manner allows histochemical detection of naphthol AS-D chloroacetate esterase in the neutrophilic cell line and in tissue mast cells, tartrate-resistant acid phosphatase in hairy cells and certain other low malignant B-cell lymphomas, in Gaucher cells, and in osteoclasts, and a specific platelet esterase in megakaryocytes and leukaemic megakaryoblasts. A broad panel of antigens is well preserved. Beside haemosiderin, cytosolic ferritin can be detected by Perls' reaction in acute phase-stimulated macrophages. Emphasis is placed on the diagnostic impact of plasma cell siderosis and lysosomal sideroblastocytosis in haemochromatosis and in alcoholism respectively. A technique is presented to discriminate mineralized and non-mineralized bone even after decalcification.