This study was conducted to observe the distribution of josamycin, a macrolide antibiotic in flounder. Josamycin was administered orally to the flounder at the dose of 100 mg 1 kg josamycin in flounder. Josamycin in blood and various organs of flounder was analyzed using reversed phase HPLC. In blood kinetics study, Cmax was shown 9.50 $mu extrm{g}$/$mell$ at 45 min. after treatment and then decreased slowly up to 8th day. Concentration of josamycin in muscle was 0.47$mu extrm{g}$/g tissue at 11th day of the treatment and 0.41$mu extrm{g}$/g tissue at 7th day for liver. The concentration of josamycin in all the tested organs except gall bladder was decreased as the time passed. On the contrary, josamycin in gall bladder was increased 3.8 times at the day of 5th compared to that of the 1st day aftreatment.