Although leukocyte common antigen is a valuable discriminant between lymphoreticular proliferations and other histologically similar neoplasms, several publications have described difficulties in adequately labeling this determinant in formalin-fixed, paraffin-embedded tissues. We studied 662 paraffinized cutaneous and non-cutaneous neoplasms for the presence of leukocyte common antigen, using an extended avidin–biotin–peroxidase complex (ABC) method, a combined ABC–peroxidase–antiperoxidase technique, and a biotin–strept–avidin procedure. Each of the three immunohistochemical techniques produced effective results in the detection of leukocyte common antigen in all malignant lymphomas, but none of them produced false-positive staining in nonhematopoietic lesions. These results suggest that antibodies to leukocyte common antigen are highly specific and that the methods employed in this study allow for excellent diagnostic sensitivity in the recognition of cutaneous lymphomas.