Rodent allergens play a significant role in the pathogenesis of asthma and allergic rhinitis, and are potent causes of acute and chronic symptoms. This has long been apparent in occupational settings, particularly in the laboratory, but has been most recently studied and found to be important in home environments. These allergens have been suggested as uniquely important among inner-city children with asthma. Furthermore, rodents have become increasingly popular as pets. With recent awareness of significant exposure in a variety of settings, hypersensitivity to rodents has become increasingly important. This review focuses on the importance of rodent allergens, concentrating on mouse and rat, but including other potentially important rodents such as gerbil, hamster, and rabbit. It also discusses the pathogenesis, diagnosis, prevention, and management of rodent allergy.