Abstract: The mechanisms leading to death from anaphylaxis after insect sting involve antigen cross-linkage of antibody molecules that activate immunoglobulin receptors on inflammatory cells. The aim of our study was to investigate the pathomorphology and the expression of C5aR in fatal anaphylaxis in a patient after a fatal insect sting. A 38-year-old women was stung by a honeybee. C5R1 expression was detected in many dilated capillaries in the lungs. Pulmonary epithelial cells did not bind the monoclonal antibody for C5R1; however, intensive cytoplasmic staining was detected in endothelial cells. The findings of this case provide evidence for an active role of complement in fatal anaphylaxis elicited by bee venom. C5aR detection could be useful in the identification of sudden death cases because of unwitnessed fatal insect sting cases. Authors can recommend this immunohistochemical analysis on all sudden unexpected deaths outdoors where a possible bee sting might occur.