Lansoprazole is a benzimidazole derivative that effectively decreases gastric acid secretion, regardless of the primary stimulus, via inhibition of gastric H+,K(+)-adenosine triphosphatase (ATPase). It provides effective symptom relief and healing of peptic ulcer and reflux oesophagitis after 4 to 8 weeks of therapy and appears to prevent recurrence of lesions when administered as maintenance therapy. When administered at therapeutic dosages, lansoprazole produced higher healing rates than ranitidine or famotidine in patients with duodenal and gastric ulcers. Lansoprazole heals duodenal ulcers more rapidly than ranitidine or famotidine. Relief of ulcer symptoms in lansoprazole recipients is at least equivalent to, and tends to be more rapid than, that in patients receiving histamine H2-receptor antagonists. In comparisons with omeprazole 20 mg/day, lansoprazole 30 mg/day produced duodenal ulcer healing more rapidly and reduced ulcer pain to a greater extent at 2 weeks, but overall healing rates were similar after 4 weeks of therapy. At therapeutic dosages, lansoprazole produces superior healing and symptom relief of reflux oesophagitis in comparison with ranitidine, and it tends to relieve heartburn more effectively than omeprazole, although both agents produce equivalent healing. Healing of peptic ulcers or reflux oesophagitis refractory to histamine H2-receptor antagonists occurs after 8 weeks in the majority of patients treated with lansoprazole, and lansoprazole and omeprazole demonstrate similar efficacy in patients with refractory peptic ulcers. In patients with Zollinger-Ellison syndrome, lansoprazole effectively controls mean basal gastric acid output. Lansoprazole is generally well tolerated in clinical trials. The incidence of adverse effects is similar to that of omeprazole, ranitidine and famotidine in comparative studies. Combination therapy with lansoprazole and antibacterial agents such as amoxicillin, tinidazole, roxithromycin and/or metronidazole appears to eradicate Helicobacter pylori in 22 to 80% of patients with this organism. Limited data also suggest that lansoprazole may have superior activity against H. pylori in comparison with omeprazole, although the clinical relevance of this preliminary finding requires further confirmation. Thus, lansoprazole may be considered as alternative to existing antisecretory agents available for the treatment of acid-related disorders, particularly because it may provide more rapid healing and relief of symptoms.