We investigated the factors influencing diel patterns in stream metabolism by measuring incident light levels, benthic CHLa and fine organic matter (FBOM), ambient nutrient levels, and water transit time and transient storage at four streams located in the Virginia Coastal Plain. Reach-scale metabolism estimates were determined using the diurnal dissolved oxygen technique and transient storage was determined by conservative tracer (Cl^-) additions. Data were collected monthly at each site during January-June 2008. Despite similar geomorphic settings, the streams exhibited divergent patterns in both the amplitude and timing of diel O₂ maxima and minima. Our results suggest that sequestration of nutrients during periods of high incident light (low canopy) resulted in higher O₂ maxima but did not influence O₂ minima. The timing of the nighttime O₂ minimum was predictable based on seasonal changes in sunrise. The timing of the daytime O₂ maximum was more variable ranging from noon to 7pm. Consistent differences were observed among sites. In this presentation, we consider the environmental factors that influence the timing of diel patterns in stream O₂ and their implications for stream NPP and R.