A　new　flow　injection　analysis　(FIA)　system　equipped　with　an　electrochemiluminescent　(ECL)　detector　has　been　developed　and　applied　for　the　ECL　detection　of　2-thiouracil.　The　FIA-ECL　system　used　a　specially　designed　flow-through　ECL　thin-layer　cell　to　reduce　the　dead　volume,　the　IR　drop　across　the　cell,　and　the　probability　of　accumulation　of　gas　bubbles　in　the　cell.　It　was　thus　envisioned　to　improve　the　detection　limit　of　the　FIA-ECL　method.　After　being　established,　the　new　FIA-ECL　system　was　used　to　investigate　the　ECL　response　of　2-thiouracil　in　the　presence　of　the　ECL　of　Ru(bpy)(3)(2+).　It　was　found　that　2-thiouracil　could　enhance　the　ECL　of　Ru(bpy)(3)(2+)　over　a　wide　pH　range　(pH　4.0-12.0).　A　highly　sensitive　method　for　detection　of　2-thiouracil　in　biological　samples　was　developed　by　the　new　FIA-ECL　system　after　optimizing　several　experimental　conditions,　such　as　the　applied　potential　of　the　working　electrode,　the　pH　value　of　the　aqueous　solution,　the　flow　rate　of　carrier　solution,　and　the　concentration　of　Ru(bpy)(3)(2+).