Circulating tumor cells (CTCs) in the blood of cancer patients have been demonstrated to be of prognostic value regarding metastasis and survival. The CellSearch(®) system has been certified for the detection of CTCs and as a prognostic tool in patients with metastatic breast, colon and prostate cancer. Few studies have evaluated the detection of CTCs originating from esophagogastric or pancreatic cancer with the CellSearch(®) system. In the present small pilot study, a total of 16 patients with either esophagogastric (n=8) or pancreatic (n=8) adenocarcinomas at various disease stages were randomly screened and included. A total of 7.5 ml of blood was drawn from each patient and analyzed for CTCs using the CellSearch(®) device. CTCs could be detected in 1 out of 8 patients (12.5%) with esophagogastric and in 7 out of 8 patients (87.5%) with pancreatic cancer. The preliminary data obtained from this observational feasibility study suggested that the CellSearch(®) system may become a valuable tool for the detection of CTCs in patients with pancreatic adenocarcinoma, whereas the usefulness in patients with early-stage esophagogastric adenocarcinoma may be limited. This study clearly points towards a requirement for larger studies focusing on patients with pancreatic adenocarcinoma at various disease stages and assessing CTCs, whereas patients with esophagogastric adenocarcinomas should be part of further pilot studies.