Vertical profiles of ozone and temperature were measured on 40 occasions during the austral spring of 1990 at McMurdo Station, Antarctica, and once again near record levels of ozone depletion were observed. Total ozone decreased from 260 DU in late August to its minimum value of 145 DU on 9 October, when the ozonesonde was at it's lower detection limit from 15 to 16.5 km. Ozone reductions were observed almost exclusively between 12 and 20 km, with a half life of 20 days. This is similar to previous years. Although McMurdo was within the polar vortex for most of the period, there were several occasions when the edge of the vortex was over McMurdo. During these periods, ozone above 20 km approximately doubled, but below 20 km remained relatively unchanged. ¿American Geophysical Union 1991