Ozone measurements from the Polar Ozone and Aerosol Measurement (POAM) experiment launched in September 1993 are compared with those from the Microwave Limb Sounder (MLS), the Halogen Occultation Experiment (HALOE), and the Stratosphere Aerosol and Gas Experiment II (SAGE II). The comparisons extend over the period from February 1994 to April 1995. POAM is in excellent agreement with the comparison instruments above 22 km. The agreement is generally in the 5--7% range and is substantially smaller than the instrumental errors. Below 22 km, POAM tends to have lower ozone densities than the other instruments, reaching differences of nearly 20% at the lowest altitudes. We discuss the implications of these low-altitude differences in the context of systematic measurement errors in the comparison instruments. The accuracy of the POAM ozone measurements is demonstrated by comparing zonal means and standard deviations of the three data sets. The large number of comparisons with satellite instruments demonstrate that the POAM ozone data are valid within the instrumental errors and that the precision and accuracy of the data are adequate for scientific investigation and interpretation.¿ 1997 American Geophysical Union