Lipopolysaccharide (LPS) and outer membrane protein (OMP) preparations of Bordetella pertussis were incorporated into multilamellar liposomes composed of soya bean-derived phospholipids which were then used for oral and intranasal immunization of mice. Specific antibody responses of animals immunized by either route were measured in lung washes. A specific IgA response to LPS was detected after immunization with the OMP-containing liposomes but not with the LPS-containing liposomes, indicating adjuvant activity of the proteins. The OMP-containing liposomes were significantly more effective in inducing immune responses than the OMP preparation alone. Responses were highest when mice were given a booster 30 days after primary immunization. Maximum responses occurred 20 days after the booster but specific antibody was still detected 75 days after the secondary immunization. These results suggest that this liposome antigen delivery system has potential in stimulating secretory antibody responses which may be helpful in protecting against infection from B. pertussis.