Vibrationally excited formyl radicals (HCO) were generated by the photolysis of acetaldehyde at 248 nm and detected by using laser-induced fluorescence (LIF). LIF via the (B) over tilde(2)A'-(X) over tilde(2)A' UV system was first used for the kinetic study of HCO. The high detectivity of the (B) over tilde(2)A'-(X) over tilde(2)A' LIF made it possible to perform experiments at low initial HCO concentrations, thereby suppressing undesirable second-order side reactions. The rate constants for the total removal of three vibrational levels of HCO ((X) over tilde(2)A', v(1),v(2),v(3) = 000, 010, 001) by O-2 have been determined to be [6.6 +/- 0.3(2 sigma)] x 10(-12), [8.7 +/- 1.5(2 sigma)] x 10(-12) and [6.3 +/- 1.1(2 sigma)] x 10(-12) cm(3) molccule(-1) s(-1), respectively. This study is the first measurement of the rate constant for the HCO(001) + O-2 reaction, An upper limit of the OH production yield was determined to be 3 x 10(-3) on the basis of a calibration of LIF intensities of HCO and OH. A comparison with previous kinetic studies is made, and the causes of the differences are discussed.