THE gram-negative anaerobic bacilli that do not bear spores have been grouped together in a genus to which the name "Bacteroides" has been assigned.1 There are many reports of human infections caused by Bacteroides, but the occurrence of such cases is not widely appreciated. During the last four years, 20 cases have been seen at this hospital (Table 1). On the basis of cases reported in the literature and those seen here, an attempt will be made to describe the clinical aspects of these infections, with the purpose of calling attention to the various conditions in which Bacteroides infection should . . .