This multicenter randomized, double-blind, 4-wk study compared the new H2-receptor antagonistic roxatidine (R) to placebo (P) for treatment of endoscopically diagnosed active duodenal ulcer disease. Subjects were evaluated after 2 and 4 wk of treatment. Those whose ulcer was unhealed at 2 wk received 2 more weeks of treatment before final evaluation. Ulcer healing (endoscopically determined) with roxatidine was more effective than placebo at both wk 0-2 (R = 33.9%, P = 21.9%, p = 0.018) and wk 2-4 (R = 68.2%, P = 29.7%, p < 0.001), with an overall 4-wk effectiveness of 78.9% compared to 44.8% (p < 0.001). At the end of treatment, average maximum ulcer diameter diminished 83% in R and 50% in P (p < 0.001). Roxatidine was also more effective than placebo in decreasing abdominal pain (p < 0.001), decreasing the number of antacid tablets taken for pain relief (p < 0.001), improving dyspeptic symptoms (p < 0.001), and permitting return to a normal routine for subjects with previous illness-imposed restrictions on -work and/or other daily activities. The profile of laboratory values and adverse experiences demonstrated roxatidine to be safe and well-tolerated. The efficacy of roxatidine as evaluated by the healing rate of duodenal ulcer and reduction in abdominal pain emphasize its value as an addition to the family of H2-receptor antagonists.