The bacterial disease of castor in the Sudan has been reinvestigated. Typically the disease symptoms are brown or black, round or angular lesions on leaves; occasionally the thin succulent branches are attacked, but not the vascular tissue.The bacterium responsible for the disease was previously thought to bePseudomonas solanacearumE.F.Sm. but comparative studies show that the Sudan species differs in pathogenicity and physiology fromP. solanacearum.It closely resemblesXanthomonas ricinicola(Elliott) Dowson (=Bacterium riciniYoshi and Takimoto) in characters, host range and pathogenic effects. In culture on solid media the growth ofX. ricinicolais typically yellow, while that of the Sudan species is dirty white; but this difference is not considered sufficient to justify the establishment of a new species.The author proposes the specific namericinioriginally adopted by Archibald (1927) and Yoshi&Takimoto (1928), for the species ofXanthomonascausing the leaf blight disease of castor, and considers that the causal organism in the Sudan is an atypical strain of this species.