A chiral overlayer was deposited on Pd(I 1 1) in ultrahigh vacuum by the adsorption of either R- of S-2-butanol. Enantio selective chemisorption onto this surface was explored by adsorption of a chiral probe, propylene oxide. It was found that the coverage of R-propylene oxide adsorbing on an R-2-butoxide-covered surface, ratioed to that on one covered by S-2-butoxide, reached a maximum value of similar to2 at a relative 2-butoxide coverage of similar to25% of saturation, and decreases to unity at a coverage of similar to50% of saturation. This implies that the enantioselectivity depends critically on coverage and arises due to chiral "pockets" formed on the surface. (C) 2003 Elsevier B.V. All rights reserved.