Mortality statistics can be compiled using underlying cause-of-death data or multiple cause-of-death data, which include other contributing causes of death.For the leading causes of death in the United States during 2000-2001, we compared underlying and multiple cause-of-death statistics.For some conditions, little difference was observed between the 2 estimates. For other conditions, up to 10 times more deaths were identified from multiple-cause data than from underlying-cause data. The 10 leading causes of death differed when using the 2 types of data.Whenever possible, underlying and multiple cause-of-death statistics should both be presented. Analyses that use only the underlying cause of death ignore additional information that is readily available from multiple-cause data, and the more limited data may underestimate the importance of several leading causes of death.