The sulfation of gastrin in serum, antrum and duodenum was studied in 22 normo- and 20 hypergastrinemic patients. The ratio between gastrin-17 and gastrin-34 was measured in antrum and duodenum. The degree of sulfation was reduced in the antrum of hypergastrinemic patients (35.3 +/- 1.3%, mean +/- SEM) compared with 48.0 +/- 2.1% in normo-gastrinemic patients (p less than 0.001). The degree of sulfation in serum and duodenum was similar to that of the antral gastrins in all patients. The percentage of gastrin-34 in antrum was increased (7.3 +/- 0.7%) in hypergastrinemic compared with 4.9 +/- 0.3% in normogastrinemic patients (p less than 0.01). In the duodenum the percentage of gastrin-34 was similar in normo- and hypergastrinemia. When classified according to clinical diagnosis, sulfation of antral gastrin was normal in duodenal ulcer (47.6 +/- 4.5%) but decreased in gastric ulcer (36.7 +/- 1.6%, p less than 0.01) and pernicious anemia (31.3 +/- 1.9%, p less than 0.001) compared with 48.2 +/- 2.2% in control patients. In pernicious anemia a larger proportion of antral gastrins occurred as gastrin-34 (8.2 +/- 0.9%) compared with 4.8 +/- 0.4% in control patients (p less than 0.01). Our study suggests that both sulfation and proteolytic processing of the gastrin precursor is diminished in hypergastrinemia of antral origin.