A total of 100 moribund and freshly dead cultured marine Mullet (Mugil cephalus), from a marine farm at Lake Temsah, was subjected to clinical and postmortem examinations. Samples were also aseptically taken for bacteriological examination. Haemorrhages and ulcers mainly at the head region beside eyes, gills, lips and operculia were observed. The majority of the affected fish showed congestion and petechiae in most of the internal organs. The isolated organisms were identified as flavobacterium spp. The isolated strain was found to be pathogenic when injected I.M. in healthy fish while I/P injection was less pathogenic.