Measurements of total ozone at Macquarie Island (55¿S, 159¿E) reveal statistically significant reductions of approximately twelve percent during July to September when comparing the mean levels for 1987--90 with those in the seventies. In order to investigate the possibility that these ozone changes may not be a result of dynamic variability of the stratosphere, a simple linear model of ozone was created from statistical analysis of tropopause height and isentropic transient eddy heat flux, which were assumed representative of the dominant dynamic influences. Comparison of measured and modelled ozone indicates that the recent downward trend in ozone at Macquarie Island is not related to stratospheric dynamic variability and therefore suggests another mechanism, possibly changes in photochemical destruction of ozone. ¿ American Geophysical Union 1992