In the preparation of chiral-supported catalysts, the immobilization process can produce changes in the behavior of the resulting resin-supported species. The polymeric matrix plays important roles that affect the activity, selectivity and stability of the final catalysts. Pseudodilution effects very often favor the activity of the supported species, and the presence of the hydrophobic matrix increases the stability of the water-sensitive active sites. The steric interaction between the polymeric backbone and the groups in the chiral auxiliary can modify, even dramatically, the stereochemical outcome of the reaction.