The temperature dependence of the overall rate constant for the C3H7O2 + NO reaction and the rate constant for the minor branching channel resulting in the production of i-C3H7ONO2 have been measured using the turbulent flow technique with high-pressure chemical ionization mass spectrometry for the detection of reactants and products. The temperature dependence of the overall rate constant for the C3H7O2 + NO reaction was investigated between 298 and 213 K at 100 Torr pressure, and the data were fit by the following Arrhenius expression (with 2 standard deviation error limits indicated): 4.3(-0.9)(+1.0) x 10(-12) exp[(268 +/- 56)/T] cm(3) molecule(-1) s(-1). This expression agrees well with previous isomer-specific measurements of the n-C3H7ONO2 and i-C3H7O2 + NO rate constants made at lower pressures. The temperature dependence of the rate constant for the minor reaction channel i-C3H7O2 + NO --> i-C3H7ONO2 was investigated between 298 and 213 K at 100 Torr pressure. The following Arrhenius expression was determined for the minor channel: 4.9(-2.9)(+5.3) x 10(-16) exp[(1380 +/-230)/T] cm(3) molecule(-1) s(-1). The Arrhenius expressions for the overall rate and the i-C3H7ONO2 producing channel indicate a branching ratio of about 0.006 at 298 K and 0.020 at 213 K at 100 Torr pressure, which is in good agreement with the predictions of a recently revised empirical model for alkyl nitrate branching ratios.