Contaminating bacteria from the oropharynx and bacteria that colonise the stomachs of patients with a high gastric pH impede the isolation of Campylobacter pylori from gastric biopsy specimens. Commercially available selective supplements are inhibitory to this organism and therefore a specific selective medium is needed for isolation. Potential selective agents were evaluated for their activity against 97 strains of Campylobacter pylori. A modification of Skirrow's medium was developed; cefsulodin (5 mg/l) was substituted for polymyxin, and amphotericin B (5 mg/l) was added to inhibit Candida spp., a common contaminant of the stomach. No strains of Campylobacter pylori were inhibited by the Campylobacter pylori selective medium and it supported the growth of all strains compared with the biopsy urease test and Gram stained smear. Colonies were slightly larger and more easily recognised on the new medium compared with those grown on chocolate blood agar. This medium greatly improves the isolation of Campylobacter pylori and could be used alone, without a non-selective medium.