In situ ozone measurements were made from the ER-2 aircraft during the 1987 Airborne Antarctic Ozone Experiment both inside and outside the ozone hole. Midday measurements from late August until late September during aircraft ascent near 53 ¿S latitude indicate no clear temporal trend in ozone mixing ratio but instead reflect the distance of the measurement from the chemically perturbed region. The measurements made within the ozone hole at 72 ¿S show altitude dependent decreases in ozone of 61% at a potential temperature of 425 K down to 39% at 365 K. Temporal trends are also calculated at various positions relative to the boundary of the chemically perturbed region to locate the region of large ozone decreases and thereby accurately locate the boundary of the ozone hole. ¿ American Geophysical Union 1989