A double-blind clinical investigation was conducted to study the effectiveness of ranitidine therapy in 52 patients with gastritis that had been confirmed by panendoscopy. Subjective weekly assessment of symptoms showed that patients receiving 300 mg of ranitidine daily for four weeks improved considerably more than those receiving placebo. In the ranitidine-treated group, symptoms completely disappeared in 20 (80%) of 25 patients and significantly improved in the other five; in the placebo group, only nine (45%) of 20 patients improved, with the remaining 11 staying unchanged (seven patients--one in the ranitidine-treated group and six in the placebo-treated group--did not return to the hospital and so were withdrawn from the study). Panendoscopy repeated in 41 patients at the end of the four-week treatment period confirmed the assessment of symptoms. No significant adverse effects were observed in patients taking ranitidine. This investigation found ranitidine to be an effective short-term treatment for patients with endoscopically proved gastritis.