The interest in mixed surfactant systems is continuously increasing. T
he development during past years has mainly been focused on the theore
tical description of mixed micelles, the coexistence of two types of m
icelle, one rich in one of the surfactants and the other rich in the o
ther surfactant, and mixtures of cationic and anionic (catanionics) su
rfactants forming systems in which vesicles and other intricate struct
ures appear. There have also been advances in the understanding of sur
factant mixtures at surfaces as well as technical applications.