Neural cell adhesion molecules (NCAM) play an important role in embryogenesis and in some tumors, especially of neuroectodermal origin. In this study, eighteen cases of invasive breast carcinoma, seven cases of sigmoid colon carcinomas and seventeen cases of the non-small cell lung carcinoma were immunostained for NCAM. The NCAM expression, usually focal, was observed in some cases only. NCAM was expressed in the membranes, in a fine granular pattern. In three cases of breast cancers, also cytoplasmic localisation of NCAM was observed, which may suggest its cytoplasmic formation. Furthermore, in three cases expression of NCAM in histologically normal ductal lobular units adjacent to invasive breast cancers without presence of this antigen in cancer tissue was observed. The immunostaining was weak or absent in sigmoid colon carcinomas. In this study we confirm observation of some authors that NCAM expression occurs in some cases of non-small cell lung carcinomas.