Two doses of nizatidine (150 mg twice daily and 300 mg at bedtime), an H2-receptor antagonist, were compared with placebo in a 12-week, multicentre, randomised, double-blind, parallel study in 466 patients with endoscopically documented gastro-oesophageal reflux disease. Antacid tablets were given concomitantly as needed for pain. Compared with placebo, nizatidine 150 mg twice daily was highly effective in rapidly reducing the severity of heartburn, regardless of oesophagitis severity at entry. Significantly greater complete mucosal healing of oesophagitis occurred after 6 weeks of therapy with nizatidine 150 mg bid (vs nizatidine 300 mg at bedtime or placebo) only in patients with erosive oesophagitis [16/68 (24%) vs 8/65 (12%)] and erosive and ulcerative oesophagitis combined [21/99 (21%) vs 10/94 (11%)]. At week 12, healing with nizatidine 150 mg bid was also significantly greater than placebo in erosive [19/68 (28%) vs 9/65 (14%)], ulcerative [10/31 (32%) vs 3/29 (10%)], and erosive and ulcerative oesophagitis combined [29/99 (29%) vs 12/94 (13%)]. These results show that twice-daily therapy with nizatidine 150 mg is very effective at relieving heartburn, and can also heal erosive and ulcerative oesophagitis. Nizatidine 300 mg at bedtime was not effective at healing oesophagitis, compared with placebo.