The　authors　describe　a　three-dimensional　(3D)　structure　composed　of　graphene　and　DNA　for　use　in　a　voltammetric　dopamine　(DA)　sensor.　The　material　was　deposited　on　a　gold　electrode,　and　the　enhanced　charge-transfer　performance　and　deposition　of　DNA　were　confirmed　by　electrochemical　analysis.　Atomic　force　microscopy　shows　the　graphene-DNA　composite　to　have　been　assembled　on　the　modified　gold　electrode.　The　modified　gold　electrode　possesses　excellent　electrocatalytic　activity　for　determination　of　DA,　best　at　a　working　voltage　of　0.1　V　(vs.　SCE).　Ascorbic　acid　does　not　interfere.　Response　to　DA　is　linear　in　the　0.1　to　100　mu　M　concentration　range,　with　a　30　nM　detection　limit　even　in　the　presence　of　1.0　mM　of　ascorbic　acid.