The presence of a gram-negative diplobacillus in corneal ulceration having the characteristics described by Petit1 in 1899 has been reported frequently in the European literature. In America, however, either the occurrence of this organism is very infrequent or its bacteriologic differentiation from the diplobacillus of Morax-Axenfeld has not been made or cases have not been reported. This report is presented because 3 cases were observed within a short time, and in 2 of the cases the corneas were obtained for histologic examination. REVIEW OF THE LITERATURE Studies of diplobacillary keratitis have been made by several observers,2 but differentiation was not made between the diplobacillus of Morax-Axenfeld and that of Petit. It has been pointed out by Gifford3 that the differentiation between the diplobacillus of Petit and that of Morax-Axenfeld could be made only by study of cultures. However, Rosenhauch,4 Oreste,5 Zade6 and Wirtz7