In this study we show by immunoblotting that B1 and B3, two newly isolated monoclonal antibodies, react with a variety of glycoproteins with different molecular weights expressed in stomach, pancreas, colorectal and breast cancers. The pattern of reactivity differed among cancers arising in different tissues, although no correlation has been observed with the histopathological characteristics of the lesion analysed. MAb B3 and MAb B1, have a limited reactivity with peritumoral tissues, whereas react very strongly with metastatic lesion. Because of the limited reactivity of these antibodies with normal tissue, MAbs B3 and B1, armed with toxin in the form of recombinant immunotoxins, can be useful in treating certain kinds of cancer such as metastatic lesions. However, until current clinical trials are completed, we will not know if they will be helpful in cancer treatment.