Patients (106) with peptic ulceration of the oesophagus, stomach and duodenum, unresponsive to 3 or more months of high-dose treatment with ranitidine, were initially given pantoprazole (40-80 mg, p.o.) daily. In 96.7% of the patients ulcers healed within 2 to 8 weeks, and in 2.3% of patients the ulcers healed within 12 weeks. In just one patient with severe oesophagitis, the lesion took more than 6 months to heal. After ulcer healing, patients (98 to date) were treated with pantoprazole (40 mg/day) as long-term maintenance therapy. Eighty-eight of the 98 patients have been taking pantoprazole for 6 months to 3 years. During maintenance therapy, peptic disease was kept in remission in most patients with 40 mg pantoprazole. Twelve patients with oesophagitis and two patients with gastric ulcers needed higher doses (80-120 mg) to control the disease. One female patient developed peripheral oedema which disappeared quickly after stopping treatment. No further drug-related adverse effects were observed. Seven patients withdrew from the study and two patients died, all for non-drug-related reasons. Routine laboratory tests remained without significant changes in all patients. Mean (+/- S.E.M.) serum gastrin levels were already elevated during the initial high-dose ranitidine treatment (128 +/- 23 pg/ml). Within one year of the start of the pantoprazole treatment, serum gastrin levels rose to 3 times normal values (189 +/- 32 pg/ml). Thereafter, no further increases in serum gastrin were observed for up to 2.5 years. Enterochromaffin-like (ECL) cell density increased very slightly from 0.19% to 0.24% within one year.(ABSTRACT TRUNCATED AT 250 WORDS)