The outstanding recognition properties of the cucurbit1;n3;uril family has led to their use in a variety of advanced applications including catalysis, mol. machines, and self-sorting systems. For the further development of self-sorting systems based on CB1;n3; we have detd. the affinity of CB1;63;, CB1;73;, and CB1;83; toward a variety of guests by UV/Vis and fluorescence titrns. and proton NMR competition expts. Binding consts. span a wide range and selectivities between the various CB1;n3; and among the guests can be quite large. The origins of the various selectivities will also be discussed.