Disasters are of interest to governments, firms and people as they can have significant impact of commercial activity, firms and people’s lives. For this reason, there is a need to measure their impact to help assess the options to prevent or to mitigate the consequences of future reoccurrences. Unfortunately, some disasters can complicate or make much more difficult the measurement or data collection exercise making even standard collection for analysis difficult. This paper uses some actual examples from past disasters (the terrorist attacks of September 11, 2001, the ice storm of January 1998 and the power outage of August 2003). All had impact on transportation and the Canadian economy. The paper will show how the impacts of the disasters were measured and their impact on the measurement process itself.