Rates of reaction of atomic oxygen (3P) with straight chain alkanes (C1-C5) and fluoromethanes (CH3F) and CHF3) have been measured at temperatures above 850 K by a laser flash photolysis-shock-tube technique coupled with atomic resonance absorption spectrometry. Measured rate constants agreed well with a recent TST calculation for O+CH4 and O+C2H6. However, a small deviation from the TST calculation was found for O+C3H8 and larger alkanes. Preferable modified Arrhenius expressions for these reactions are presented. A good Evans-Polanyi correlation was found for the reactions investigated in the present study.