Xenografted human pancreatic tumors (5 ductal adenocarcinomas, 1 leiomyosarcoma, altogether 26 samples) were investigated about their immunohistochemical expression of epidermal growth factor receptor (EGFR), somatostatin (SS) and bcl-2 protein. The expression of the EGFR varied from tumor to tumor. One originally negative carcinoma became immunoreactive during passagings, one tumor has lost its early positive expression, and in 3 cancer lines a phenotypically constant pattern was seen. SS immunoreactivity was practically absent in all tumor samples. Concerning bcl-2 expression, different staining patterns were observed among the carcinomas, but the leiomyosarcoma has retained its strong positivity during xenograftings. In the PZX-5 carcinoma line that was originally negative, the one month Sandostatin treatment induced the strong expression of bcl-2 protein suggesting a development of an acquired resistance against programmed cell death in this tumor.