Separations of basic drug enantiomers have been investigated using glucuronyl glucosyl beta -cycloclextrin (GUG beta -CD) as a chiral selector in the background electrolyte by capillary zone electrophoresis. The effects of GUG beta -CD concentration and running buffer pH on the migration times and resolution of 16 basic drug enantiomers were precisely examined using a linear polyacrylamide-coated capillary. High resolution of 16 basic drug enantiomers was generally attained with a running buffer pH 2.5 or 3.5 containing 10 mm GUG beta -CD. Next, we compared the chiral resolution abilities of GUG beta -CD with those of beta -CD and maltosyl beta -CD (G2 beta -CD). GUG beta -CD showed higher resolution for basic drug enantiomers tested than beta -CD and G2 beta -CD. This could be due to that hydrogen bonding or ionic interactions of uncharged and charged glucuronyl glucosyl groups of GUG beta -CD with an analyte could stabilize the inclusion complex.