In the past 3½ years, 55 strains of gram-negative, nonfastidious, anaero-genic, facultatively anaerobic rods of the species Erwinia herbicola have been isolated from patients and other hospital sources. Characteristics, isolation, recognition, and differential diagnosis of the group are outlined. Many strains exhibit a yellow pigment which facilitates their recognition. Nonpigmented strains may present particular diagnostic problems.