The aim of this study was to determine immunohistochemical markers that give, a positive reaction with malignant mesothelioma or primary pulmonary adenocarcinoma and investigate the specificity and sensitivity rates of these antibodies. Twelve malignant mesotheliomas and 8 primary pulmonary adenocarcinoma cases were examined using pan-CK, HMWCK, LMWCK, EMA, Ber-EP4, CD 15, vimentin, CEA, surfactan, calretinin, thrombomodulin antibodies. Histochemical analysis was performed with the PAS, PAS-diastase stains. According to our results calretinin and thrombomodulin showed positive reactivity with a high sensitivity and specificity rate. Vimentin can be included in immunohistochemical panels as an antibody reacting positively for malignant mesothelioma. CEA and CD15 which are believed to be very strongly positive for pulmonary adenocarcinoma, showed low specificity and sensitivity rates in this investigation.