The aim of this study was to estimate the levels of serum gastrin in a group of patients with either ulcerative colitis or Crohn's disease and to compare the results with those of a group of normal controls. In 108 consecutive patients with IBD (66 with ulcerative colitis, 32 with Crohn's disease and 10 with indetermined colitis) serum levels of gastrin were measured by radioimmunoassay. One hundred and eight normal people were served as controls. The levels of serum gastrin were significantly elevated in patients with Crohn's disease compared to normal controls (74.4 +/- 43.9 pg/ml vs. 47.5 +/- 32.4 pg/ml, P<0.05), irrespectively of the activity of the disease. On the contrary, patients with ulcerative colitis exhibited no significant differences compared to normal controls. Differences between Crohn's disease and ulcerative colitis patients were statistically significant (P<0.001). The rate of infection by Helicobacter pylori in patients with inflammatory bowel disease was statistically significantly lower as compared with normal controls (31.7% vs. 55.1%, P<0.001). It is concluded that patients with active or inactive Crohn's disease have increased levels of serum gastrin. This may have implications concerning the high incidence of upper GI lesions found in patients with Crohn's disease despite the very low incidence of Helicobacter pylori infection.