Nuclear DNA content was determined by image analysis of paraffin-embedded tissue sections in 20 cases of resected pancreatic ductal adenocarcinoma. Seven cases (35%) showed a diploid pattern; 13 (65%) were aneuploid. Mean survival time of patients with diploid tumors was significantly greater (17 months) than for patients with aneuploid carcinomas, 7.5 months (P < .03, Kaplan-Meier and Cox univariate analysis). Patient age, grade of differentiation, primary tumor size and lymph node status did not correlate significantly with ploidy pattern and survival. In four cases atypical hyperplasia/adenocarcinoma in situ was present in the main duct epithelium at the pancreatectomy resection line. These intraductal foci were uniformly diploid. We conclude that despite the uniform fatality of pancreatic cancer, adenocarcinomas with aneuploid patterns pursue a significantly more rapid and aggressive clinical course than do diploid tumors and that the atypical intraductal epithelial foci that may accompany resected specimens from invasive adenocarcinoma are DNA diploid, may represent noninvasive precursor lesions and are of uncertain clinical significance.