Objective: Immunohistochemical detection of CD15 is important in diagnosis of Hodgkin lymphoma and may be relevant in classification of renal tumours. In four tests with 71-121 participating laboratories conducted by the Nor-diQC external quality assessment scheme only 50-76 % of CD15 stains were sufficient, mainly because of too diluted primary antibody concentration, insufficient HIER and less successful antibody clone. The purpose of this study was to evaluate three anti-CD15 antibodies based on vendor and inhouse optimized protocols.