1. The bacteria which caused "putrid-skin" disease in Hypophthalmichthys mo-litrix and Aristichthys nobilis are similar to Pseudomonas putida of the common carpsand Salmon fishes. Artificial infection with bacteria isolated from diseased fish causethe same disease in healthy Hypophthalmichthys molitriax and Aristichthys nobilis as wellas in Misgurus fossilis. 2. Symptoms of the disease appeared as follows: at the first stage of the dis-ease, red spots appeared on the skin, then the epidermis putrified and scales felloff, exposing the dermis; the inner margin of the focus was inflamed and the scalessurrounding the focus became loose, displaying a plain mark; as the case progressed,the dermis also putrified and disintegrated, making a deep pit in the skin. In excep-tionally rare cases putrification penetrated deep into the muscle, exposing skeletonand viscera. Observations on the sections of focus showed that the internal organswere not effected. 3. This disease is a menace to fish production. If it occurs during the growthperiod of parent fishes, it will effect the accumulation of nutritive material anddevelopment of gonads, causing great disadvantage to artificial propagation and fryproduction as well as to food fishes. 4. The lowest inhibiting effective concentration of four antibiotics in vitroranges as following: Aureomycin 0.39μg/ml., Chloromycin 0.78μg/ml., Neomycin1.56μg/ml., Streptomycin 3.12μg/ml. 5. The effective lethal concentration of four bactericides (mercurous nitrate,mercurous acetate, mercuric nitrate and bleaching powder) in vitro at 25℃ in 24hours ranges as following: mercurous nitrate, mercurous acetate,mercuric nitrate allat 1/10,000,000; bleaching powder at 1p. p. m. 6. As a measure for prophylaxis, in summer, attention should be paid to thequality of water, prevention of pollution and addition of fresh water. After parturi- fication or infection, Hypoghthalmichthys molitriw and Aristichthys nobilis should betreated with aureomycin or chloromycin in peritoneal or muscular injection with adosage of 5mg./kg. At the same time spraying pond water with bleaching powder,making it containing a concentration at 1 p.p.m. will also be of good help in earlystages of infection.