The reaction between the OH radical and furfural and the first stages of the subsequent processes have been investigated in detail. The model proposed for the overall kinetics has been verified by means of linear and nonlinear fittings up to the millisecond range. The identification of the intermediates has been based on ab initio optimized production enthalpies, as well as on the comparison of semiempirically predicted electronic transitions with the spectra observed after pulse radiolysis. The radical attack produces a radical adduct to the ring in position 5, k = (4.7 +/- 0.8) x 10(9) M-1 s(-1), which in sequence undergoes first a beta-cleavage, k = (4.7 +/- 2.4) x 10(5) s(-1), and then a 1-6 hydrogen transfer, k = (3.4 +/-1.3) x 10(4) s(-1). The final decay to a very low absorbing molecule occurs through a second-order reaction, k = (3.0 +/-0.5) x 10(8) M-1 s(-1).