Fifty-one patients were treated with 20-60 mg omeprazole for reflux oesophagitis resistant to H2-blocker therapy during a mean of 49 months of follow-up. With use of a standardized enzyme-linked immunosorbent assay technique specific IgG and IgG Helicobacter pylori antibodies were determined in serum obtained at the start of therapy and at the most recent visit. At the start of therapy 26 patients (51%) had evidence of H. pylori infection, as demonstrated by increased IgG and IgA antibody levels. During follow-up, 4 of these 26 patients (15%) became H. pylori seronegative. It is concluded that long-term treatment with omeprazole has no effect on H. pylori status in most patients.