AbstractThis report compares a direct, peroxidase conjugated antibody method with a peroxidase labeled streptavidin/biotin (LSAB) method for the detection of immunoglobulins A, G and M, complement (C3c), fibrinogen and kappa and lambda light chains in neutral buffered, formalin fixed, paraffin embedded renal biopsy tissue.Twenty-five percutaneous renal biopsies were selected and 2μm serial sections cut. These were deparaffinized, rehydrated, blocked for endogenous peroxidase, and digested with 0.025% protease type VIII for 3 min. Detection efficiencies of the primary antibodies were determined by checkerboard titrations, and optimal dilutions of each antibody were applied for 1 hr at room temperature. Antibody binding sites in both methods were detected with 3,3′diaminobenzidine tetrahydrochloride (DAB).Both methods detected similar distributions and quantities of immune reactants in each biopsy. A greater detection efficiency was achieved for each antibody with LSAB, and the intensity of the reaction products was similar for both methods. The direct antibody method used fewer reagents and took 1 hr less than the LSAB. (The J Histotechnol19:125, 1996)