A discharge flow reactor coupled to laser-induced fluorescence and mass spectrometry, for the detection of ethoxy and nitrate radicals, respectively, has been used to study the kinetics of the reactions of C2H5O and C2H5O2 with NO3 at ca. 1 Torr of helium and 298 K. From the analysis of the C2H5O concentration-time profiles in two sets of experiments, the reactions C2H5O + NO3 --> C2H5O2 + NO2 (1) and C2H5O2 + NO3 --> C2H5O + NO2 + O-2 (2) were observed to be strongly coupled. The rate constants were derived from modeling calculations, k(1) = (3.3 +/- 0.9) x 10(-12) cm(3) molecule(-1) s(-1) and k(2) = (2.3 +/- 0.5) x 10(-12) cm(3) molecule(-1) s(-1). These data are compared with other very recent literature data, and their atmospheric significance for nighttime chemistry is briefly discussed.