Both singlet and triplet potential energy surfaces for the reaction of ground-state formaldehyde (CH2O) and ozone (O-3) are theoretically investigated at the BMC-CCSD//BHandHLYP/6-311+G(d,p) level. Various possible isomerization and dissociation pathways are probed. Hydrogen abstraction, oxygen abstraction, and C-addition/elimination are found on both the singlet and the triplet surfaces. The major products for the total reaction are HCO and HOOO, which are generated via hydrogen abstraction. The transition state theory (TST) and multichannel RRKM calculations have been carried Out for the total and individual rate constants for determinant channels over a wide range of temperatures and pressures.