The year 1997 was notable for the record low ozone column densities observed between 20°S and 60°S. The Ozone Analysis System (OASYS) has been used to investigate low ozone events during 1997 at Macquarie Island (55°S, 159°E). OASYS uses satellite ozone data to generate three-dimensional ozone mixing ratio analyses. The analyses were compared with data from the Macquarie Island ozonesonde program. OASYS was able to reproduce the vertical ozone profile, although it was on average 10 to 15 per cent lower than the ozonesonde profile in the lower stratosphere. This is caused by a systematic difference between satellite and ozonesonde data, and is accentuated when the satellite data is not available. OASYS was used to examine three low ozone events at Macquarie Island in winter, spring and early summer. The winter event is dominated by vertical motion in the lower stratosphere, while the spring and early summer events are dominated by horizontal advection of low ozone either from the polar vortex, or the remnants of the Antarctic ozone hole.