We evaluated the importance of hyporheic zones for nitrogen loss in three streams in conjunction with the Wyoming LINX-2 ¹⁵N-NO₃ + Chloride tracer tests in summer 2005.  Land use in the streams varied from reference to suburban/agriculture.  Hyporheic zones were sampled for conservative and ¹⁵N tracers before, during and after the LINX-2 experiments via wells installed in stream banks.  Hyporheic exchange was minimal in suburban/agriculture streams as evidenced by little to no tracer in wells.  In contrast, hyporheic exchange was observed in the reference stream.  Only a small portion (<1%) of the tracer that reached this hyporheic zone was denitrified.   These results suggested that while the reference stream had greater exchange, N loss via denitrification was substrate limited, while the potential for hyporheic processing in the suburban/agriculture streams was limited by hydrologic exchange.  We tested this idea using hyporheic injections of ¹⁵N-NO₃ and bromide with and without added DOC in the reference the suburban streams.  Our hypothesis was supported in that 1) the suburban stream had high potential for denitrification in both hyporheic injections, and 2) the reference stream had higher denitrification rates with added DOC compared to the ¹⁵N addition alone.