The carbon cycle of the Kuparuk River, a meandering tundra stream, is dominated by inputs of eroding peat and leaching dissolved organic carbon from the tundra. Net production of epilithic algae is about 13 g C∙m−2∙yr−1, an order of magnitude less than inputs of allochthonous particulate organic carbon and two orders of magnitude less than inputs of dissolved organic carbon. The streamwater has a mean total organic carbon concentration of 6.8 mg∙L−1, and the annual export of organic carbon from the watershed is 2–3 t∙km−2∙yr−1; both are similar to the average for temperate streams. However, because of the low primary productivity of tundra vegetation, the export of organic carbon from the watershed via the river is a larger fraction (2–6%) of the total watershed net primary production than the 0.1–0.4% usually found for temperate rivers.