Flow system measurements are reported of the approximate rate constants for the gas phase reactions Si+ + O2 → SiO+ + O, SiO+ + N → Si+ + NO or NO+ + Si, and SiO+ + O → Si+ + O2. The constants are, respectively, −11, ∼1.5 × 10−10, ∼1.5 × 10−10, and 2 × 10−10, all in cm3 s−1.