The kinetics of the title reactions were investigated using the laser photolysis - resonance fluorescence method, employing the sequential two-photon dissociation of NO2 in the presence of H-2 as the OH source. The 298 K rate constant for OH + C3H8 was found to be (1.15 +/- 0.1) x 10(-12) cm(3) s(-1), in excellent agreement with the literature recommendation, and with a separate determination using HNO3 photolysis at 248 nm as the OH source. The 298 K rate constants for OH + n C3H7I and i-C3H7I were measured for the first time and found to be (1.47 +/- 0. 08) and (1.22 +/- 0.06) x 10(-12) cm(3) s(-1), 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 n-C3H7I and i-C3H7I, which has implications for the reactive iodine budget of the marine boundary layer.