The application of affinity capillary electrophoresis (ACE) to the stu
dy of molecular interactions is reviewed. ACE appears to be a sensitiv
e, versatile and convenient tool to obtain reliable data on binding co
nstants and stoichiometries of interacting systems using the Hummel-Dr
eyer method and variants thereof. A powerful feature is the possibilit
y to analyze simultaneously the affinity of a large number of compound
s for the same ligand, making it a promising tool for the screening of
large combinatorial libraries.