The reaction rates for CH and CD with O-2 have been measured for temperatures between 293 and 720 K. The rate constant has a slight negative temperature dependence which can be well fit over the temperature range by (4.7 +/- 0.2) x 10(-11)(T/293)(-0.22+/-0.1) cm(3) molecule(-1) s(-1). The deuterium isotope effect has been measured to be k(H)/k(D) = 1.16 +/- 0.06 at 293 K and is approximately constant to within experimental error between 293 and 720 K. The isotope effect and the temperature dependences can be described by a barrierless addition with no collisional stabilization of the adduct before dissociation to products. The effects of the known species HCO2 and HOCO are not evident in the CH + O-2 reaction rate constant at these temperatures and pressures. Simple transition state theory can model the kinetic isotope effect if the transition state for addition involves a weakening of the C-H bond from the free CH molecule.