Simultaneous in situ measurements of NO, NO2, O3, and temperature were made from approximately 20 to 31 km in the stratosphere during July August, and November. Two of the balloon flights were made from Palestine, Texas (32¿N), the third from Gimli, Manitoba (50¿N). NO was detected using the chemiluminescence technique; NO2 was photolyzed to NO prior to detection. Both the NO and NO2 mixing ratios are in good agreement with most other measurements in this altitude region. To within the combined uncertainties the measured NO2 to NO ratios agree with those calculated assuming photo chemical steady state. There is, however, a tendency for the observed ratio to be larger than the calculated ratio at low altitudes near 32¿ but not at 30¿N. Refinements to the experiment will be required to elucidate discrepancies. From the observation of a temporal increase in the sum of NO and NO2 while at constant altitude, it is possible to infer the abundance of N2 O5 near noon. Further, a lower-limit estimate of the total odd nitrogen mixing ratio of 16-19 parts per billion by volume near 30 km is made using the observatrions of NOx, the estimated N2O5 mixing ratio, and previous measurements of HNO3.