Intrapancreatic extension of pancreatic duct cell carcinoma in 19 resectable cases was evaluated by both hematoxylin and eosin (H&E) staining and quick immunostaining using antibodies against cancer-associated antigens--e.g., CA19-9, DUPAN 2, and CEA--on the intraoperative frozen-section biopsy during the course of laparotomy. By H&E staining, malignant lesions were identified in four of 19 cases (21%). By the immunostaining method, however, cancer cells were detected in 10 of 19 cases (52.6%). This immunostaining method was particularly useful in defining cancer cells surrounded by dense fibrous connective tissue, in which cancer cells are usually difficult to evaluate by H&E staining. Thus, the application of such immunostaining, together with H&E staining, on the cryostat sections of biopsy specimens may provide important information for the appropriate operative method. Retrospective study of permanent sections revealed that pathological diagnosis by quick immunostaining was more accurate than diagnosis by H&E staining.