The consistency of contemporary stratospheric ozone photochemistry is examined in the light of recent data from the Nimbus 7 satellite. Temperature, O3, H2O, HNO3, and NO2 data from the limb infrared monitor of the stratosphere experiment and CH4 from the stratospheric and mesospheric sounder experiment are used in conjunction with a simplified photochemical model to compare calculated and observed O3 for 30¿N during March. The photochemical model underestimates the ozone in the upper stratosphere by 15-32%. Calculated and observed mixing ratios of NO2 and OH and the daytime value of the ratio HNO3/NO2 are presented. Results from a Monte Carlo analysis of the uncertainty due to errors in the input data are also given. The sensitivity of the model results to modification of certain key reaction rate constants is studied. These changes result in higher ozone mixing ratios in the upper stratosphere, which are in better agreement with the data. The effect of such modifications on other photochemical parameters is shown. The level of agreement between theory and observations with regard to the temperature sensitivity of O3 and the diurnal variations in O3 is discussed.