Liposomes of stable multilamellar type, which previously demonstrated great efficiency in antibiotic transport, were used in this study as transport vehicles of antigenic extracts of Brucella melitensis (HS: complex of lipopolysaccharide/phospholipids/outer membrane proteins). The incorporation of HS into positively charged liposomes produced a protective effect against experimental murine brucellosis when they were administered 1 day before or 2 days after infection, as the number of colony-forming units in the spleen was reduced in relation to the untreated control group (P < 0.01). On the other hand, the use of HS-free or bound in liposomes with negative net charge did not produce a significant effect. Moreover, the incorporation of HS into cationic liposomes eliminated the toxicity of the lipopolysaccharide.