The absolute yields of the stable carbon-containing products CO, CO2, and H2CO formed in the reaction of triplet methylene (X B-3(1) = CH2) with O2 have been determined using a flash kinetic spectrometer. CH2 radicals were generated by excimer laser photolysis of ketene, and product formation was monitored by time-resolved infrared diode laser absorption. The reaction was carried out in a static gas cell at room temperature (T -298 +/- 3 K) with total pressures in the range 1-25 Torr. The measured product yields were as follows : CO, 0.34 +/- 0.06; CO2, 0.40(+0.09/-0.07); H2CO, 0.16 +/- 0.04. The rate constants for production of CO and CO2 were equivalent to the published rate constant for removal of CH2. Additionally, indirect evidence indicated that the yield of OH is 0.30 +/- 0.05.