Despite radical surgical treatment, the prognosis of patients with pancreatic cancer is poor. The success of surgical treatment is often limited due to local recurrence and especially the development of metastases and peritoneal carcinosis by cells which have been seeded already at the time of operation. Immunocytological methods enabled the detection of disseminated cancer cells before their clinical manifestation as demonstrated by this study. Lavage samples from the peritoneal cavity and bone marrow samples from 34 patients with an adenocarcinoma of the pancreas were investigated with a panel of six different monoclonal antibodies against tumor-associated antigens (CEA, CA-19-9, 17-1A, C-54-0, Ra96) and cytokeratin, respectively. Additionally, 43 patients with benign diseases were investigated as a control group. By this method, micrometastases were detected either in the bone marrow or the peritoneal cavity in 76% of pancreatic cancer patients. The occurrence of stained cells in the peritoneal cavity and bone marrow samples correlated with the tumor stage and showed even in early stages (I and II) a detection rate of 43% (bone marrow) and 33% (peritoneal cavity), respectively. No unspecific reactions were found in the control group. The 1-year follow-up shows a significant correlation between tumor cell detection and the survival (p = 0.03). Our study demonstrates that in most patients pancreatic cancer is a disseminated disease at time of diagnosis. It underlines the need for adjuvant postoperative therapy concepts.