The bactericidal activity of the fluméquine, a synthetic derivative of the « quinolones » family, has been recently recognized and has resulted in its common use in human and veterinary medicine. The availability of an artificial model of trout furunculosis allowed to test its curative properties in Aeromonas saimonicida infection. For this purpose, we have used 2 species of trout (Salmo gairdneri and S. trutta), and 2 pathogenic strains of which LD 50 ranged initially from 400 to 800 bacteria/fish, intramuscularly (IM). Fish, divided in 3 groups, received respectively 20 g, 40 g an 80 g of Flumix (fluméquine powder with 3 % of active component) per 100 kg of b.w./day during 6 days, representing 1, 2 and 4 times the mammalian dose. The drug was stuck on dry pellets supplied twice a day as 1 % of b.w. Fingerlings were arranged in 30 subjects groups maintained in 15°C flow-through tanks, and experimentally infected by IM injection of about 1 or 10 LD 50. A preliminary administration of 200g/100kg of fish of Flumix was done on a sample during a fortnight and did not result in any observation of acute toxicity. A conspicuous protective effect of the drug was noticed in all cases the treatment was carried on at the same day as the infection. Differences between mortality percentages in controls and treated fish were about 60 p. 100, whatever the trout species ant the bacterial strain. Variations were of trifling importance according to the therapeutic doses, and when testing fish with high doses of pathogen ([MATH] 10 LD 50) the effect seemed better, resulting of the higher mortality of controls. In some cases, the treatment was started 20 hours after inoculation of Aeromonas. Except in one case, the protection was then very lowered, and this has been ascribed to the loss of appetite of diseased subjects In conclusion, the efficacy of fluméquine treatments in control of furunculosis is stated and some practical indications are given. The dose of 40g/100 kg of fish of fluméquine powder (40 g/kg of food when feeding at 1 %) is recommended for fish, diet being distributed in 2 meals, and the rules of every other antimicrobial treatments being respected