A theoretical study on the kinetics of the H2CO + O-2 -> HCO + HO2 reaction has been carried out from first principles using canonical variational transition state theory incorporating corrections from small curvature tunneling and hindered rotation treatments. Rate constants were calculated using the geometries, gradient and Hessian obtained at the BH&HLYP/cc-pVDZ level with the energy correction at the CCSD(T)/aug-cc-pVTZ//BH&HLYP/cc-pVDZ level. The rate constant expression is obtained as k(t) = 2.95 x 10(-21) x T-3.152 x exp [-18352/T] (cm(3) molecule (1) s (1)) for the temperature range 300-3000 K. The result shows an excellent agreement with available scattered experimental data over this temperature range and thus the expression can be used confidently for the whole range. (C) 2008 Published by Elsevier B.V.