A method of emulsifying asphalt using a polyamine polybetaine, preferably a dibetaine, as an emulsifier or co-emulsifier and an emulsion of asphalt, water and a polybetaine, preferably a diamine dibetaine. The advantages of using a polyamine polybetaine as an emulsifier or co-emulsifier include its ability to provide superior cationic and anionic emulsions, and slow-setting emulsions at low use levels, and the excellent adhesion of the cured asphalt film.