The second phase of the Antarctic Concordiasi campaign was carried out in the austral spring of 2010 to study ozone and polar stratospheric clouds, gravity waves over the Antarctic peninsula, and data assimilation in numerical weather prediction models using observations made from stratospheric superpressure balloons. For the first time, GPS radio occultation measurements were made from these stratospheric balloons to provide atmospheric profiles of refractivity. Dropsondes were also deployed for assessing the quality of satellite data assimilation over the Antarctic. We compare the GPS Radio occultation measurements near the Antarctic Peninsula with refractivity derived from nearby dropsondes and the Méteofrance ARPEGE model. The objective is to determine whether the GPS radio occultation technique has the potential to provide sufficiently high quality estimates of Antarctic atmosphere profiles of temperature, to be helpful with model validation. The GPS radio occultation profiles are measured with respect to precise geometric height, so there is some uncertainty when mapping the dropsonde measurements of temperature and relative humidity to refractivity as a function of pressure to geometric height. Given the refractivity profiles from dropsondes and the model, raytracing was used to simulate the GPS signal excess phase, excess Doppler shift and bending angle due to the refractive bending in the atmosphere, for comparison with the observations. The first profiles show a close agreement between model simulations and observations of Doppler shift, down to the lowest level of 2.2km above the ellipsoid. The two balloons equipped with GPS radio occultation systems flew a combined total of 107 days within the Antarctic polar vortex, and recorded more than 700 occultations, a comparable number of profiles to the 647 dropsondes released by the 13 balloons equipped with driftsonde systems during the campaign.