['Previous studies have demonstrated greater efficacy for omeprazole compared with cimetidine in patients with endoscopically verified oesophagitis, but excluded the substantial group of gastro-oesophageal reflux disease (GERD) patients with reflux symptoms but without endoscopic abnormality. This prospective, randomized, double-blind study compared omeprazole and cimetidine in the treatment of GERD-associated heartburn both in patients with symptomatic non-ulcerative oesophagitis and in those with heartburn but without oesophagitis.', 'A total of 221 patients with heartburn and oesophageal mucosa grade 0 (normal, n = 51), 1 (no macroscopic erosions, n = 52), 2 (isolated erosions, n = 97) or 3 (confluent erosions, n = 21) were randomized to receive double-blind either omeprazole 20 mg daily or cimetidine 400 mg q.d.s. for a period of 4 weeks. Those still symptomatic after 4 weeks of treatment received omeprazole 20 mg daily for a further 4 weeks.', 'There was no correlation between severity of heartburn and endoscopic grade at entry (correlation coefficient = 0.196). After 4 weeks of treatment, the proportion of patients in whom heartburn was controlled (no more than mild symptoms on no more than 1 day in the previous 7) on omeprazole (66%; 74/112) was more than double that on cimetidine (31%; 34/109) (P < 0.0001). There was no significant difference between the relief of heartburn in the 47% of patients without unequivocal oesophagitis (endoscopic grade 0 or 1) and in the 53% of patients with erosive oesophagitis (grade 2 or 3) (P = 0.31). Only treatment with omeprazole (P < 0.0001) and lower severity of heartburn at entry (P < 0.01) were significant in predicting heartburn relief. Amongst those patients requiring an additional 4 weeks of treatment with omeprazole, 67% (54/81) reported that their heartburn was controlled after 8 weeks of treatment.'] Is omeprazole more effective than cimetidine for the relief of all grades of gastro-oesophageal reflux disease-associated heartburn , irrespective of the presence or absence of endoscopic oesophagitis?