Ozone sounding profiles will be used to analyse the ozone distribution in the Antarctic vortex collar region. The collar region will be defined based on the gradient in the potential vorticity field calculated from ECMWF ERA-Interim reanalysis data. The sounding profiles will be classified into vortex collar and in-vortex cases. Additionally the data will be divided according to equivalent latitude. Ozone soundings have been made in Marambio (64S, 57W), on the Antarctic Peninsula, since 1988, i.e. soon after the discovery of the Antarctic 'ozone hole'. The ozone sounding record at Marambio now covers more than two decades of nearly continuous ozone profile data. The vortex edge is often located close to Marambio. Data from other Antarctic sounding stations and Earth observation data will be used to increase the number of observations from the collar area. The analysis will be supported by data from the FinROSE chemistry-transport model, which will be driven by the ERA-Interim winds and temperatures.