The occurrence of chronic gastritis and intestinal metaplasia (IM) was studied in 257 patients with gastric carcinoma (GC). In all cases biopsies were available from the benign mucosal area adjacent to the tumor, and in 139 patients from the antrum and/or body mucosa outside the tumor. The results were compared with endoscopically and bioptically examined noncancer controls representing a large Finnish population sample. For every GC patient, a control subject was matched by age and sex. In addition, a mean age-adjusted score (AAS) of chronic gastritis, which expresses the progression of gastritis in GC patients as compared with that in the general population, was calculated for GC patients. The prevalences of chronic and atrophic gastritis in the antrum and body mucosa were similar in GC patients and controls when carcinoma cases were not more specifically classified according to histologic type or location of tumors. On the other hand, the location of the tumor showed a significant relation to gastritis: the progression of gastritis was more rapid (high mean AAS value) and the prevalence of atrophic gastritis was higher in the tumor-affected area (i.e., in the antrum in patients with antral [distal] tumors; in the body in patients with body [proximal] tumors), than in the general population, but were similar in the tumor-free area in both GC patients and controls. In the intestinal type of GC (IGC), the prevalence of chronic gastritis was higher and its progression was more rapid than in controls. In the diffuse type of GC (DGC), these correlations were less distinct. In GC patients, the IM adjacent to and outside the tumor area was significantly more common and extensive than in the corresponding area of controls, and a significant positive correlation was present between the location of the tumor and the distribution of IM. Like gastritis, the IM showed a closer relationship to IGC than to DGC. In all cases of GC and particularly of IGC, the antral mucosa tended to be more severely affected by gastritis and IM than the body mucosa, i.e., the prevailing type of gastritis found in this GC series was that morphologically corresponding to the so-called B-type of chronic gastritis.