With the possible exception of inbred mice, the identification of laboratory animals has been in a state of anarchy until very recently. In a letter to the editor of LABORATORY ANIMAL CARE (19: 121-123, 1969), Mr. Samuel Poiley outlined the general principles of a system of nomenclature being developed by the Committee on Nomenclature of the ILAR. This journal requires that authors use standard terminology for rats and mice as listed in the ILAR publication ANIMALS FOR RESEARCH. We welcome the following report which represents a system of nomenclature for outbred animals and publish it as a service to the scientific community. Authors of papers submitted to this journal will be expected to identify their animals by this system. We urge the editors of other scientific publications to consider the merits of adopting standard terminology to end the reign of confusion in animal identification.