The reactions of 1and 2butyne with O(3P) were studied at 298 K by means of a CO laser resonant absorption technique. The CO formed. O(3P)+CH3CH2CCH→CC3 H6H3CH2CH+CO. O(3P)+CH3CCCH3→CH3C C3H6CH3+CO. From the kinetic modeling of the observed rates of CO formation, the rates of these reactions were found to be 5.0 × 1011 and 1.6 × 1012 ml.