Nitrite dynamics could be highly associated with forest N cycles. However, they have often been overlooked mainly because of the experimental difficulties that occur owing to chemical reactive nature of NO 2 − . We investigated NO 2 − dynamics in an N-saturated forest soil with a recently developed method using 15 N. Soils were aerobically incubated for 145 h after 15 NO 2 − addition, and changes in 14 N and 15 N concentrations of NO 2 − , NO 3 − , NH 4 + , and dissolved organic N (DON) were monitored. Simultaneous production and consumption of NO 2 − were observed. The turnover rate of NO 2 − was even faster than that of NH 4 + and NO 3 − calculated in other studies. Of the added 15 NO 2 − , 28.5% was oxidized to NO 3 − and 17.8% was incorporated into the DON pool within 4 h. The remainder might be emitted as gas or fixed by insoluble soil organic matter. Our results suggested that rapid NO 2 − turnover could be a major driving force for N transformations in forest soil.