Histamine H2-receptor antagonists at conventional doses have proved only partly efficacious in the treatment of reflux oesophagitis. The aim of this study, therefore, was to compare the efficacy of high doses of nizatidine (300 mg b.i.d.) versus placebo in 117 patients with grade I and II oesophagitis. After 6 weeks' treatment, 70.6% of nizatidine-treated patients showed complete endoscopic healing against 25.4% of placebo-treated subjects (p less than 0.001). After 12 weeks, the respective healing rates were 77.5% and 47.4% (p less than 0.01). Nizatidine also proved significantly more effective than placebo in improving overall symptoms (p less than 0.05). Antacid intake was significantly greater in the placebo group (p less than 0.001). Both treatments were well tolerated. In conclusion, this study demonstrates that nizatidine at the dose of 300 mg b.i.d. for 6-12 weeks constitutes an effective treatment for patients with reflux oesophagitis.