The irradiation of dialkyl ketones in cyclohexene leads to the formation of cyclohexenyl-dialkylcarbinols. The use of aldehydes leads to the formation of the corresponding secondary alcohols, but the reaction is more complex because of concomitant Kharasch addition which can, however, be suppressed. The mechanism of the alcohol formation has been elucidated by the use of an optically active substrate, carvomenthene, and has been shown to involve the intermediacy of a cyclohexenyl radical. The structure and genesis of a biscarbinol by-product is discussed.