The safety and immunogenicity of a 'new' oral B subunit-whole cell (B-WC) cholera vaccine based on recombinantly produced B subunit was evaluated in Swedish volunteers. The recombinant B-WC vaccine was comparable to the 'old' type of B-WC vaccine in inducing IgA and IgG antitoxin antibody responses as well as vibriocidal antibody responses in serum, which are known to be good serological correlates of the gut mucosal IgA antitoxic and antibacterial immune responses after oral immunization with B-WC vaccine. Neither of the two B-WC vaccines was associated with any significant side-effects. The results indicate that the more easily and cheaply produced recombinant B subunit can replace the 'old' type of B subunit isolated from cholera toxin for use in the oral B-WC cholera vaccine.