We examined whether immunization with a newly developed oral cholera vaccine would elicit gut-derived antibody-producing cells in the blood and in distant mucosal tissues, such as the minor salivary glands, in 30 adult Swedish volunteers. The results of this study demonstrated that this vaccine indeed induced production of specific antibody-producing cells against the cholera toxin B subunit in both peripheral blood and salivary glands. The response in blood, which after primary and booster immunizations comprised both immunoglobulin A (IgA) and IgG antibody-forming cells, was highly transient and preceded the response in salivary glands; the latter response was restricted to the IgA isotype. The results provide further evidence of the existence of a common mucosal immune system in humans. Furthermore, these findings support previous observations that in animals, the cholera toxin B subunit may be a useful carrier protein for preparing enteric vaccines against pathogens encountered at intestinal and extraintestinal mucosal sites.