We performed short-term (24-hour) additions of ¹⁵-N enriched nitrate in nine different streams in Oregon.  Streams were classified as urban, agricultural, or reference based on riparian vegetation and watershed land use.  All streams were nitrogen-limited (molar N:P ratios <22.5:1) with varying basin areas (22 – 3300 ha) and discharges (2 – 118 L/s).  We sampled biotic and physical parameters to determine the short-term fate of the isotopically-enriched nitrate.  Dentrification to either N₂ or N₂O was detected only at low levels in 5 of the 9 streams.  Urban streams with high standing stocks of in-channel primary producers (filamentous algae and macrophytes) and high total dissolved nitrogen removed up to 99% of ¹⁵N-nitrate from transport.  However, this represented less than 1% of the total flux of nitrogen in these streams. In contrast, agricultural and reference streams with higher standing stocks of terrestrial detritus and lower total dissolved nitrogen removed 8 - 47% of the ¹⁵N tracer from the water column, representing 5 - 20% of total nitrogen flux.  The positive relationship between nitrate uptake and total dissolved nitrogen concentration indicate stream networks are unable to maintain natural patterns of nitrogen transport in the face of human disturbance and elevated nutrient inputs.