Prospective randomized study on the effect of ranitidine against injection ulcer after endoscopic injection sclerotherapy for esophageal varices. Thirty-five consecutive patients undergoing endoscopic injection sclerotherapy for esophageal varices were randomly allocated to either ranitidine-administered group (18 patients) or ranitidine-nonadministered group (17 patients), in an attempt to evaluate the efficacy of ranitidine for prevention and healing of postinjection ulcer with a prospective randomized trial. Two of seventeen patients in the nonadministered group dropped out of this trial because of development of gastric ulcer, so 18 patients in the first group were evaluated and compared with the 15 remaining patients in the second group. Sclerotherapy was performed with 5% ethanolamine oleate and 0.6% polydocanol; the mean number of injection courses and the mean amount of sclerosant were the same in both groups. Moreover, there was no significant difference between the two groups in either the occurrence rate or the size of injection ulcer 1 wk after the last session. However, the persistence rate of ulcer 1 month after last injection in the ranitidine-administered group was significantly lower than that in the ranitidine-nonadministered group (6.3% vs. 38.5%, p less than 0.05). Our study demonstrated that ranitidine administration will help to hasten healing of postinjection ulcer, although it was not effective for prevention of injection ulcer. 