In about 80% of Bangladeshi volunteers a single oral or intramuscular immunisation with a new cholera toxoid immunogen (B subunit) gave rise to a local intestinal secretory immunoglobulin A (IgA) antitoxin response as measured in intestinal-lavage fluid by enzyme-linked immunosorbent assay methods. The rise in IgA antitoxin titre was similar for both immunisation routes and was comparable to that seen after clinical cholera; however, the response persisted longer after oral than intramuscular immunisation. A second immunisation by either route evoked an antitoxin response which usually closely resembled that seen after the first immunisation.