The relative importance of O2, NO3-, organic carbon, and acidity on denitrification was studied in a full 26 factorial experiment. Soils were collected from two forested watersheds (WS) (disturbed and reference) and at two slope positions (stream-bank and hillside). Combinations of four incubation treatments (with and without H2O flooding, NO3- amendment, glucose amendment, and at ~pH 5 or ~pH 6) were applied in a full factorial design. An ANOVA of N2O production during 24-hr aerobic incubations under 10 kPa acetylene revealed that all main effects were significant. Flooding with H2O increased N2O production by three orders of magnitude in disturbed WS soils exhibiting high ambient NO3-. Both flooding and NO3- amendment were necessary to increase N2O production in reference WS soils exhibiting low ambient NO3-. Glucose amendment increased N2O production in the mineral soil sampled at 6-15 cm depth more than in the 0-6 cm sample. Carbon limitation is probably unimportant for denitrification in surface horizons at Coweeta, but C-limitation occurs with increasing soil depth. Although acid treatment had a minor inhibitory effect on denitrification rates, acid forest soils apparently support denitfifier populations capable of appreciable NO3- reduction. For. Sci. 33(1):135-144.