Eels were kept in experimental tanks w ith aerated tapw ater at temperatures of 23~ 27 e . T he weig ht per fish w as 200~ 300g. The eels w ere fed medicated feed by syringe. T he dosage of Ox ytet racycline ( OTC) w as 200mg/ kg b. w . per day for 5 days. Muscle and liver tissues were taken from five eels at hours 0, 6, 12, 24, 48, 72, 120, 168, 216 af ter the last dose w ith OTC. Tissues samples w ere homogenized w ith 4% t richloroacet ic acid - 0. 02mol/ LNa2HPO4 aqueous solut ion and trichloromethane, fat w as removed by pet roleum ether. The aqueous layer was purified by a C18 solid-phase ext ract ion column. The OTC residues w ere determined by HPLC external standard method using a SGE- ODS- 5 L 250 @ 4. 0mmID column w ith a mobile phase of methano-l acetonit rile-DMF-buffer ( Na2EDTA-citric acid-sodium cit ratew ater) = 1B1. 2B0. 42B1. 9 at UV detect ionwavelength of 360nm. The OT C level in eel muscle reached 1. 0mg/ kg at 24 hours and decreased to 0. 1mg / kg at 168 hours ( 7 days) after w ithdrawal.