Rate coefficients for the reaction between ground-state O atoms and methylacetylene have been measured using the High-Temperature Photochemistry (HTP) technique at temperatures from 300 to 1350 K and pressures from 100 to 700 mbar. The oxygen atoms were generated by flash photolysis of O-2 or CO2 and their relative concentrations were monitored by time-resolved resonance fluorescence. The data are independent of pressure and are well-fitted by the expression k(300-1350 K) = 2.9 x 10(-11) exp(-1134 K/T) cm(3) molecule(-1) s(-1) with 2 sigma precision limits of +/-6% to +/-12%, depending upon temperature, and corresponding 2 sigma accuracy limits of about +/-22%. An estimation for methyl group H-abstraction yielded k(H)(300-2500 K) = 5.7 x 10(-20)(T/K)(2.16) exp(-2429 K/T) cm(3) molecule(-1) s(-1). This suggests that addition is the only significant initial O-atom attack step even at temperatures as high as those encountered in atmospheric-pressure methylacetylene-air flames.