Cytologic examination of peritoneal washings was performed in 40 patients with pancreatic ductal adenocarcinoma (35 head, 5 body) whose tumors had been selected as potentially resectable by computed tomographic (CT) findings. Saline (100 mL) was instilled and aspirated at laparoscopy in 27 patients and at laparotomy in 13. Malignant cells were found in the peritoneal washings in 12 of 40 patients (30%): 29% in cancers of the pancreatic head versus 40% in the body; 33% at laparoscopy versus 23% at laparotomy; and in 4 of 8 patients with ascites versus 8 of 32 without ascites. The cytology was positive in 6 of 8 patients (75%) who had a prior percutaneous needle biopsy versus 6 of 32 (19%) of those who did not (p less than 0.01). Liver metastases were found in six patients, all with negative cytology. One of 10 pancreatic head cancers with positive cytology was resectable versus 13 of 25 with negative cytology (p less than 0.05). Survival was significantly longer in patients with negative cytology. We conclude that (1) pancreatic cancer sheds malignant cells into the peritoneum early and commonly; (2) laparoscopic lavage is an effective means of cytologic study; (3) ascites is not a precondition for cytologic study, nor does its presence necessarily imply carcinomatosis; (4) intraperitoneal spread of cancer cells may be promoted by tumor biopsy; (5) cytologic findings provide an additional index of resectability; and (6) cytologic findings appear to correlate with duration of survival. This study shows that even "localized" pancreatic cancer is often not contained and suggests caution with biopsy of potentially curable lesions.