Rodent problems on the North American Continent are highly varied as they are on most other continents and involve both introduced as well as native species. Many of the species found in North America have counterparts of the same family or closely related genera on other continents, and the problems they cause or damage they do is often similar. Rodent problems can be categorized in many ways, but for the purpose of this chapter they will be discussed on the basis of taxonomic classification and how they affect man’s interest or impact on humans.