This invention generally relates to cationic oil-in-water emulsions that can be used to deliver negatively charged molecules, such as an RNA molecule. The emulsion particles comprise an oil core and a cationic lipid. The cationic lipid can interact with the negatively charged molecule thereby anchoring the molecule to the emulsion particles. The cationic emulsions described herein are particularly suitable for delivering nucleic acid molecules (such as an RNA molecule encoding an antigen) to cells and formulating nucleic acid-based vaccines.