MAS (Millimeter-wave Atmospheric Sounder) observations from the shuttle ATLAS spacelab pallet have revealed some little known (and unexplained) structure in stratospheric ozone mixing ratio profiles at sub-polar latitudes, of both hemispheres. Qualitatively similar features are observed by UARS instruments. Another possibly related feature has been observed by ground-based remote sensing from the South Pole over an extended season. In all these cases, it seems likely that active photochemistry and highly structured horizontal and vertical transport play important roles. Some evidence of a similar feature is also present in a current 2-D photochemical model. This high latitude phenomenon is both an intriguing challenge for current 3-D models and potentially useful test for validating remote sensing experiments. ¿ American Geophysical Union 1996