Immunofluorescent (IF) and immunoperoxidase (PAP) technics have a lot in commum in the detection of cellular and tissue antigens. In renal diseases they have been used in the detection of immunoglobulins and immune complexes. In the present paper the authors compare the technics of IF and PAP in paraffin sections to frozen renal biopsy sections by in 25 cases. There was significant correlation between IF of frozen renal biopsies with PAP of paraffin sections for immunoglobulins. There was on correlation for complement components and fibrinogen as well as for IF on paraffin sections for all components investigated. IF in paraffin sections was inadequate for the detection of deposits in renal glomeruli when perfomed in routine sections.