Electrochemical concentration cell (ECC) ozonesondes flown by NOAA and NASA Wallops Flight Facility (WFF) personnel during the Stratospheric Ozone Intercomparison Campaign (STOIC) conducted at the Jet Propulsion Laboratory's Table Mountain Facility, Wrightwood, California, July 21 to August 1, 1989, exhibited highly similar ozone measurement precisions and accuracies even though considerably different methods were used by the two research groups in preparing the instruments for use and in calibrating the instruments. The Table Mountain data as well as data obtained in the past showed the precisions to range from about ¿3 to ¿12% in the troposphere, remain relatively constant at ¿3% in the stratosphere to 10 mbar, then decrease to about ¿10% at 4-mbar pressure altitude. Corresponding ozone measurement accuracies for individual ozonesonde soundings were estimated to be about ¿6% near the ground, decrease to -7 to 17% in the high troposphere where ozone concentrations are low, increase to about ¿5% in the low stratosphere and remain so to an altitude of about 10 mbar (~32 km), then decrease to -14 to 6% at 4 mbar (~38 km) where ozone concentrations are again low. Stratospheric ozone measurements were also made during STOIC with ground-based lidars and a microwave radiometer that will be used for ozone measurements in the future at sites of the Network for the Detection of Stratospheric Change (NDSC). The ECC ozonesonde observations provided useful comparison data for evaluating the performance of the lidar and microwave instruments. ¿ American Geophysical Union 1995