The coccobacillus of Perez is of practical interest because of its supposed role in the ozena stage of atrophic rhinitis. It has been isolated from ozena by Horowitz, Perez, Hofer, and in this country by Horn and Ward.1 So far the reports have not dealt extensively with the characteristic of the organism, and in this article I wish to give briefly the principal results of a study of several strains both from European sources and obtained here from patients. Nasal exudates are inoculated in broth tubes, which are incubated for 15-20 hours, when subcultures are made on other mediums. I have found that this is a good method because the Perez bacillus practically outgrows the other organisms introduced into the broth. The following statements are based on the detailed study of 12 strains selected from 50 isolated altogether.