Recent measurements of the rates for reactions of NaO2and NaOH with HCl and of the photoabsorption cross section of NaCl allow for realistic estimates of the impact of sodium chemistry on chlorine partitioning in the upper stratosphere. When sodium chemistry is incorporated into our one‐dimensional model of the upper atmosphere, the results indicate that the calculated ClO concentrations near 50 km could increase by up to a factor of two with a corresponding decrease in calculated O3abundances of as much as 15 percent. The impact on ClO and O3depends crucially on the assumed meteoritic source of sodium, on transport from the mesosphere, and on transformation and removal of gaseous sodium in the stratosphere. Since the fluctuations in the abundance of gaseous sodium could induce O3variations comparable to those caused by changes in temperature and solar UV, consideration of the chemistry of sodium and other metals may be an important element in efforts toward early detection of trends in upper stratospheric O3. Future increases in stratospheric chlorine will magnify the impact of sodium species on ozon