In the presence of BF3 the reaction rate of organocopper and cuprate reagents with poorly reactive epoxides is dramatically enhanced. Lithium organocuprates are the best choice among the various organocopper and cuprate reagents tested. Even the dimesityl cyanocuprate is able to react with cyclohexene oxide in excellent yield. No products of cationic rearrangements are observed. The reaction with various epoxides shows a complete stereochemical (pure anti opening) and regiochemical control (attack on the less hindered side of the epoxide).