The　electrochemical　oxidation　and　electrochemiluminescent　behavior　of　homogentisic　acid　(HGA)　has　been　studied　in　aqueous　solutions　over　a　wide　pH　range　by　linear　sweep　voltammetry,　cyclic　voltammetry,　chronocoulometry　at　a　glassy　carbon　electrode,　by　controlled　potential　electrolysis　at　a　large　area　spectroscopic　graphite　electrode,　and　by　spectroelectrochemistry　at　an　optically　transparent　drilled　holes　graphite　(DHG)　electrode　in　a　thin-layer　cell.　The　studies　reveal　that　the　electrochemical　oxidation　of　HGA　at　carbon　electrodes　is　a　reversible　process　involving　two-　electron,　two-proton　transfer.　In　addition　to　the　electrochemical　oxidation,　the　chemical　oxidation　of　HGA　by　dissolved　oxygen　was　investigated　by　spectroscopic　method　combined　with　voltammetry.　It　was　revealed　that　HGA　is　fairly　stable　in　strongly　acidic　media　but　readily　oxidized　by　dissolved　oxygen　in　alkaline　media　giving　rise　to　1,4-benzoquinone-2-　acetic　acid,　the　same　product　as　that　of　electrooxidation　of　HGA.　This　oxidation　product　is　stable　in　acidic,　neutral　and　weakly　alkaline　media,　but　can　further　degrade　in　strongly　alkaline　media　yielding　oxalate　as　the　final　product.　The　electrochemiluminescent　mechanism　of　HGA　in　the　presence　of　Ru(bpy)32+　at　a　glassy　carbon　electrode　was　also　investigated　in　detail,　based　on　which　a　sensitive　ECL　method　for　determination　of　HGA　was　developed,　and　the　detection　limit　was　3.0　x　10-8　mol　L-1.