The　plasma　kinetics　of　ciprofloxacin　(CF)　were　investigated　in　the　eels　after　administration　by　oral　gavage　and　bath　treatment.　Plasma　concentrations　of　CF　were　determined　by　high-performance　liquid　chromatography　with　fluorescence　detection.　The　mean　concentration　time　data　after　oral　gavage　of　a　single　dose　(10.0　mg/kg　CF)　and　after　bath　treatment　by　exposure　(10　μg/ml　CF)　to　medicated　water　for　48　h　were　both　best　fitted　by　a　one-compartment　model.　After　oral　gavage　in　eels,　the　half-time　of　absorption　(T1/2Ka)　was　0.10　h,　the　half-time　of　elimination　(T1/2Ke)　was　51.87　h,　and　the　maximum　plasma　concentration　(Cmax)　was　0.4552　μg/ml　at　Tmax　0.88　h.　After　bath　treatment,　the　T1/2Ka　was　0.02　h,　the　T1/2Ke　was　15.46　h,　and　the　Cmax　was　0.1175　μg/mL　at　Tmax　0.22　h.　©　2005　Elsevier　Inc.　All　rights　reserved.