The kinetics of the title reactions were investigated using the laser photolysis - resonance fluorescence method, employing the sequential two-photon dissociation of NO<sub>2</sub> in the presence of H<sub>2</sub> as the OH source. The 298 K rate constant for OH + C<sub>3</sub>H<sub>8</sub> was found to be (1.15 ± 0.1) × 10<sup>-12</sup> cm<sup>3</sup> s<sup>-1</sup>, in excellent agreement with the literature recommendation, and with a separate determination using HNO<sub>3</sub> photolysis at 248 nm as the OH source. The 298 K rate constants for OH + <i>n </i>- C<sub>3</sub>H<sub>7</sub>I and <i>i </i>- C<sub>3</sub>H<sub>7</sub>I were measured for the first time and found to be (1.47 ± 0.08) and (1.22 ± 0.06) × 10<sup>-12</sup> cm<sup>3</sup> s<sup>-1</sup>, respectively. The errors include an assessment of systematic error due to concentration measurement, which, for the propyl-iodides was minimised by on-line UV-absorption spectroscopy. These results show that reaction with OH is an important sink for <i>n </i>- C<sub>3</sub>H<sub>7</sub>I and <i>i </i>- C<sub>3</sub>H<sub>7</sub>I, which has implications for the reactive iodine budget of the marine boundary layer.