The reaction of OH radical with C2H5CN has been studied using various quantum chemistry methods. The geometries were optimized at the MP2/6-311G (d, p) and BHandHLYP/6-311G (d, p) levels. The single-point energies were calculated using G3(MP2) and BMC-CCSD methods. Both hydrogen abstraction and addition/elimination mechanisms have been investigated. The kinetics of this reaction were studied using the TST and multichannel RRKM methodologies over a wide temperature range of 150-3000 K. The calculated results indicate that alpha-H abstraction channel is the most feasible at lower temperatures. At higher temperatures, the C-addition step leading to stable intermediate C2H5C(O) NH (IM2) is apparently dominant. (C) 2008 Elsevier B.V. All rights reserved.