Rodents are commonly used for inhalation toxicology studies, but until recently the nasal passages have often been overlooked or only superficially examined. The rodent nose is a complex organ in which toxicant-induced lesions may vary, depending on the test compound. A working knowledge of rodent nasal anatomy and histology is essential for the proper evaluation of these responses. Lack of a systematic approach for examining rodent nasal tissue has led to a paucity of information regarding nonneoplastic lesions in the rodent nose. Therefore, slides from the National Toxicology Program (NTP) and the Chemical Industry Institute of Toxicology (CIIT) were examined, and the literature was reviewed to assemble the spectrum of nonneoplastic rodent nasal pathology. Presented are lesions associated with the various types of epithelia lining the rodent nasal cavity plus lesions involving accessory nasal structures. Even though there are anatomic and physiologic differences between the rodent and human nose, both rats and mice provide valuable animal models for the study of nasal epithelial toxicity, following administration of chemical compounds.