A Lagrangian chemical model is used to simulate the formation of the Antarctic ''ozone hole'': the decrease in high-latitude southern hemisphere ozone between mid-August and mid-September of each year. The model benchmark simulation of HNO3, ClONO2, ClO, and ozone for September 17, 1992, is in good agreement with UARS observations. Simulations of the ozone column over the years 1979--1994 show quantitative agreement with the secular decline in Antarctic ozone and change in the area of the ozone hole as observed by the total ozone mapping spectrometer (TOMS). The model calculates that the Antarctic ozone loss and ozone hole area both increased linearly with time after the early 1970s until the early 1990s. After the early 1990s the growth of the area of the ozone hole slows as a result of the slowing of the growth rate of total inorganic chlorine. A hypothetical doubling of the 1992 atmospheric chlorine amount would expand the ozone hole to the very edge of the polar vortex. ¿ American Geophysical Union 1996