We investigated nitrogen and phosphorus uptake in three streams in the South Fork Eel River watershed with drainage area ranging from 0.58 – 17 km². We measured uptake at a range of nitrogen and phosphorus concentrations and assessed interaction of these nutrients with a series of addition experiments. In each stream, NH₄, PO₄, NO₃ and a cocktail of all three were added, with conservative tracers, on consecutive days. This method allowed us to estimate ambient uptake lengths and to assess stream response to increased nutrient levels. In all streams, N uptake was higher than P uptake, suggesting N limitation. Addition of P did not affect N uptake in any of the three streams, but N addition increased P uptake in the two smaller streams. The magnitude of increase in P uptake length with increasing P input decreased with DA, while the magnitude of increase in N uptake length with increasing N input increased with DA. These results suggest the availability of N relative to P increases with DA, consistent with an observed increase in N:P in the water column. We hypothesize a decrease in the severity of N limitation, consistent with observed increases in nitrogen-fixing biomass as streams increase in size.