Quantum chemical calculations have been employed to determine the structures and energetics of the radicals arising from the OH addition to alpha-pinene and beta-pinene. The rate constants of OH addition to alpha-pinene and beta-pinene are calculated using the canonical variational transition state theory (CVTST). At the B3LYP/6-31G(d,p) level of theory, the high-pressure limit rate constants at 300 K are 5.1 x 10(-11) cm(3) molecule(-1) s(-1) for alpha-pinene and 6.1 x 10(-11) cm(3) molecule(-1) s(-1) for beta-pinene, consistent with experimental studies. These results provide the isomer-specific rate constants and branching ratios for OH addition to alpha-pinene and beta-pinene. (c) 2005 Elsevier B.V. All rights reserved.