Fixation techniques were investigated for their ability to preserve morphology, esterase activity and cell surface antigens in paraffin-embedded mouse lymphoid tissue. The avidin-biotin-peroxidase system was used to stain antigens Thy-1.2, Lyt-1, Lyt-2, RA32C2 and F4/80. Conventional fixatives were compared with fixatives containing periodate and lysine plus paraformaldehyde and/or glutaraldehyde. Conventional fixatives preserved esterase activity but not many cell surface antigens. Periodate-lysine fixatives allowed better preservation of membrane antigens, but esterase activity was often lost at antigen-preserving concentrations of paraformaldehyde or glutaraldehyde. However, a periodate-lysine fixative containing both paraformaldehyde and glutaraldehyde preserved esterase and showed good to excellent staining of Lyt-1, Thy-1.2, RA32C2, and F4/80. Lyt-2 could not be stained with any fixative, but was well preserved in frozen material post-fixed with periodate-lysine based fixatives. We conclude that with proper fixation immune cell surface markers can be identified in paraffin-embedded tissue.