Although there has been much argument over the impact of variable inflation rates upon economic performance, there has been surprisingly little attempt to define the term "variability of inflation" carefully or to test proposed hypotheses connecting variability and the level of inflation. Precise definitions are given in the paper and a model is constructed showing that the level/variability hypothesis may be formulated in terms of the presence of heteroscedasticity in a regression model. This theoretical model is used to criticize existing studies, while an empirical study with Australian data illustrates the application of the approach.