Measurements of net ecosystem exchange (NEE) are described over a temperate coniferous forest in The Netherlands. The data show no loss of night-time fluxes at low values of friction velocity. Measurements of concentration profiles show a wide diurnal range in concentration values (50ppm) during July in the summer compared to November in the late autumn (10ppm). This is a result of photosynthetic activity during summer. The profiles also show the effect of respiration in the build up of the night-time profiles. The half-hourly day time NEE shows a relation with incoming short-wave radiation when separate classes of specific humidity deficit are defined. Quantum yield varies from 0.0197 to 0.0375. A linear relation was found between NEE and surface conductance at the ecosystem level. The annual carbon sequestration of the forest in 1997 is 338gm−2 per year. It was estimated that respiration contributed 1221gCm−2 per year to the NEE. This brings the gross primary production (GPP) of this forest to 1559gCm−2 per year. The forest shows a clear growing season (positive uptake) of 249 days, but even during the winter the forest acts as a sink for a few hours around noon.