Ozone measurements from 1970 to 1984 from the Nimbus 4 backscattered ultraviolet (BUV) and the Nimbus 7 solar backscattered ultraviolet (SBUV) spectrometers show significant decrease in total ozone only after 1979. The downward trend is most apparent in October south of 70 ¿S in the longitude zone 0¿ to 30 ¿W where planetary wave activity is weak. Outside this longitude region, the trend in total ozone is much smaller due to strong interannual variability of wave activity. This paper gives a phenomenological description of ozone depletion in the Antarctic region based on vertical advection and transient planetary waves.