Young Octopus joubini and Octopus briareus (30-60 days old) developed skin ulcers when reared in groups in high density culture.  The condition always appeared first on the dorsal mantle, eventually spreading to the rest of the mantle, and even to the head and arms of O. briareus. The first manifestation of the disease was a slight darkening of the normally translucent epidermis, followed by malfunction and destruction of the chromatophore organs in the dermis.  This resulted in clear areas that progressively enlarged and ulcerated.  The bases of the ulcers were filled with cells resembling amebocytes.  Untreated animals usually died within four days of the first signs of infection. In successfully treated animals, low cuboidal epithelial cells covered the surface, overlying a thickened dermis devoid of chromatophores, but containing some amoebocyte-like cells.  Smears taken from active lesions were cultured; they produced five bacteria: Vibrio alginolyticus, Pseudomonas stutzeri, Aeromonas hydrophila, Aeromonas sp., and Vibrio parahemolyticus. Bacteria could be seen by light microscopy and scanning electron microscopy. Healthy O. joubini were re-infected with cultures of the first four bacteria at 10⁶ concentrations and Vibrio alginolyticus produced similar skin damage within two days.  Penicillin, chloramphenicol, minocycline and furanace (Nifurpirinol) were evaluated for treatment as continuous baths and/or periodic dips.  Octopus joubini in the early stages of infection that were dipped twice a day for ten minutes in furanace (15 ppm in sea water) showed improvement and healing within ten days. Octopus briareus also showed improvement and healing but died of apparent toxic shock reaction to furanace at 20 ppm; lower concentrations were found to be effective and safe. Octopuses reared in individual containers in the same culture system were uninfected. Recommended prophylaxis is to rear octopuses individually or in lower densities and to separate and treat them with furanace at the first signs of skin damage.