Evidence for an apparent chemical depletion of ozone was observed in the Arctic polar vortex during February 1989 in the form of a depleted layer in the ozone mixing ratio altitude profile. The measurements of the distribution of ozone partial pressure in the polar vortex were conducted with ECC ozonesondes which covered the altitude range from 1 to 30 km. These balloon measurements demonstrated a depleted layer in the profile at altitudes from 18 to 24 km. The meteorological ozonesonde balloon ascents took place from January 24 to February 22, 1989 from Alert, Canada at 82.5 N. A comparison of the late February ozone profiles with the late January ozone profiles indicates that the depletion was due to a process which may have occurred while the polar air was partially in sunlight. The depleted layer was similar to that observed from the South Pole base in the Antarctic inside the ozone hole in mid-September. The depletion may have commenced at high altitudes above 22 km and moved downwards during February in a manner similar to the process in September in the Antarctic. Polar stratospheric clouds were previously observed in mid-January over the altitude regime from 16 to 24 km. ¿ American Geophysical Union 1990