PGE2 plays an important role in gastric cytoprotection. Previous experience has shown that H2-blocker drugs may have a role in gastric cytoprotective mechanisms. The effects have been compared of ranitidine and famotidine on PGE2 content in duodenal ulcer patients. Twenty patients were treated for 4 weeks as follows: group A, ranitidine (150 mg twice daily); group B, famotidine (40 mg daily). The patients underwent EGDS before and after therapy. The results show that both famotidine and ranitidine significantly increase the PGE2 content of fundic mucosa (from 112.3 +/- 73 to 210.7 +/- 106 ng/g wet wt and from 109.6 +/- 52.4 to 230.2 +/- 104.6 ng/g wet wt, respectively) in duodenal ulcer patients (p less than 0.01). Similarly, the PGE2 content of duodenal mucosa significantly increases after famotidine treatment (from 51.9 +/- 27.5 to 105.3 +/- 55.6 ng/g wet wt) as well as ranitidine treatment (from 53.8 +/- 24 to 172.6 +/- 72.9 ng/g wet wt) (p less than 0.01). It is concluded that these drugs play an important role in gastric and duodenal cytoprotection.