The alkaline phosphatase anti-alkaline phosphatase method of staining can be used to localize antigens in a variety of specimens including paraffin sections, cell smears, and cryostat sections. The immunoalkaline phosphatase precedure is especially useful when staining specimens high in endogenous peroxidase activity. Utilizing three reagents- the primary antibody, the secondary bridging antibody, and the alkaline phosphatase anti-alkaline phosphatase comples (APAAP) a highly efficient system is formed.