This study is an empirical examination of Australian auditors' interpretation of selected key uncertainty expressions such as virtual certainty, expected, reasonable assurance and possible, contained in Australian accounting and auditing standards. The results showed three major findings. First, auditors demonstrated a reasonably high degree of variability in the interpretation of uncertainty expressions. In view of the proliferation of uncertainty expressions within international and Australian accounting and auditing standards, this lack of consistency in interpretation of uncertainty expressions raises some serious concerns. Second, compared with the less experienced auditors, the more experienced auditors demonstrated greater variability in their interpretations of uncertainty expressions. Third, contrary to expectations, this study did not find any difference in judgements between auditors in big-five and non-big-five firms. In aggregate, the findings of the study have implications for standard setting.