To investigate the effect of the location of the ulcer crater on the serum levels of pepsinogen I (PGI), pepsinogen II (PGII) and the ratio of PGI/PGII, these parameters were determined in 161 healthy controls, 29 patients with gastric ulcer in the gastric body (GU-I), 65 with coexistent gastroduodenal ulcer (GU-II), 104 with gastric ulcer in the prepyloric region (GU-III), and 116 with duodenal ulcer (DU). Serum PGI levels were significantly higher (P < 0.01) in patients with GU-III (110.6 +/- 65.1 ng/mL), GU-II (100.0 +/- 46.6 ng/mL), and DU (92.2 +/- 35.2 ng/mL) than in the controls (77.4 +/- 31.4 ng/mL), while there were no significant differences between GU-I (82.5 +/- 36.3 ng/mL) and the controls. Patients with gastric ulcer in any region had significantly higher (P < 0.01) serum PGII levels (GU-I, 20.0 +/- 15.7 ng/mL; GU-II, 15.5 +/- 10.9 ng/mL; GU-III, 14.3 +/- 10.0 ng/mL) than the controls (10.6 +/- 6.0 ng/mL) and the patients with DU (10.0 +/- 5.5 ng/mL), whereas no significant differences existed between the latter two. The ratio of PGI/PGII in GU-I (5.86 +/- 3.90) was significantly lower (P < 0.01) than any other group (controls, 8.83 +/- 4.70; GU-II, 8.33 +/- 4.99; GU-III; 9.64 +/- 6.13; DU, 10.45 +/- 4.49), while patients with DU it was significantly higher (P < 0.01) than any other groups. These findings indicate that peptic ulcer is comprised of a heterogeneous group of diseases.(ABSTRACT TRUNCATED AT 250 WORDS)