Chemo-, regio-, and stereoselectivity have been achieved in the oxidations of aryl olefins. The aryl olefins were oxidized by 2 equivalents of H2O2 in acetic acid, catalyzed by 0.02 equivalent of RuCl3, leading to the formations of syn-aryl glycol monoesters. As the reaction is concerted, both the regio- and stereoselectivity are excellent. In the presence of aliphatic C=C bonds, the aryl C=C bonds were selectively dioxygenated. This represents the first example of chemoselective dioxygenation of aryl C=C bonds.