Partial pressure (p CO₂) and flux to the atmosphere of carbon dioxide ( CO₂) were studied in northern alpine and forest lakes along a gradient of dissolved organic carbon (DOC) content . Sixteen lakes were each sampled three times over the course of the ice-free season, and an additional 35 lakes were sampled once at midsummer. p CO₂ data were acquired in the field by a headspace equilibration technique. Most lakes were supersaturated with CO₂ along the entire DOC gradient, with relatively small seasonal differences. p CO₂ was positively correlated to DOC content, reflecting a close dependence between allochthonous DOC input and heterotrophic respiration in the lakes. Fluxes of CO₂ to the atmosphere were estimated from the p CO₂ measurements. Benthic respiration was indicated to be important for CO₂ emission in lakes with high DOC concentrations. In lakes with low DOC concentrations, pelagic mineralization alone was sufficient to account for a large part of the estimated fluxes.