We present a compilation and analysis of N2O data from the deep-water zone of the oceans below 2000 m. The N2O values show an increasing trend from low concentrations in the North Atlantic Ocean to high concentrations in the North Pacific Ocean, indicating an accumulation of N2O in deep waters with time. We conclude that the observed N2O accumulation is mainly caused by nitrification in the global deep-water circulation system (i.e., the conveyor belt). Hydrothermal and sedimentary N2O fluxes are negligible. We estimate the annual N2O deep-water production to be 0.3¿0.1Tg. Despite the fact that the deep sea below 2000 m represents about 95% of the total ocean volume, it contributes only about 3--16% to the global open-ocean N2O production. A rough estimate of the oceanic N2O budget suggests that the loss to the atmosphere is not balanced by the deep-sea nitrification and pelagic denitrification. Therefore an additional source of 3.8Tg N2Oyr-1 attributed to nitrification in the upper water column (0-2000 m) might exist. With a simple model we estimated the effect of changes in the North Atlantic Deep Water (NADW) formation for deep-water N2O. The upper water N2O budget is not significantly influenced by variations in the N2O deep-water formation. However, the predicted decrease in the NADW formation rate in the near future might lead to an additional source of atmospheric N2O in the range of about 0.02--0.4 Tg yr-1. This (anthropogenically induced) source is small, and it will be difficult to detect its signal against the natural variations in the annual growth rates of tropospheric N2O. ¿ 1999 American Geophysical Union