Serial serum CA 19-9 assays were performed in 30 consecutive patients who underwent resection for pancreatic cancer. Patients with preoperative CA 19-9 levels < 200 U/ml had significantly better prognosis than those with CA 19-9 > 200 U/ml (P < 0.001). Serum tumor marker normalized in 14 patients after tumor resection, and survival in this group was significantly higher than that of patients with persistently elevated CA 19-9 (P < 0.0001). Prognosis was also influenced by absence of lymph node metastases (P < 0.02) and radicality of resection (P < 0.005). Elevation of serum CA 19-9 levels after operation well predicted tumor recurrence from 1-10 months before clinical and radiological evidence. CA 19-9 determination is useful as a prognostic index after resection for pancreatic carcinoma and as a surveillance test in monitoring the efficacy of treatment.