There has been much recent interest in understanding biotic and abiotic controls on S and N cycling during winter. The objective of this study was to investigate winter sinks for SO₄^2- and NO₃^- to better understand controls on these acidifying anions during snowmelt. In February 2004, an isotopic tracer solution was applied to the snowpack at the Hubbard Brook Experimental Forest in New Hampshire. The tracer consisted of 93% atom ³⁴S applied as H₂³⁴SO₄ and 99% atom ¹⁵N applied as NH₄¹⁵NO₃. Additionally, Br^- was added (as LiBr) as a conservative tracer. The chemistry and isotopic composition of throughfall, snow, snowmelt, and forest floor leachates were monitored for one year following the addition of the chemical and isotopic tracers. The snowpack reached a maximum depth shortly after the tracer addition and melted during a three-week period ending on 22 March 2004. Nearly all (89%) of the Br^- added to the snowpack surface was recovered in the snow lysimeters during spring melt. Both SO₄^2- and NO₃^- behaved conservatively in the snowpack, much like Br^-, with 90% of the added SO₄^2- being recovered in the snow lysimeters and 100% the NO₃^-. As expected, Br^- was also conservative as it leached through the forest floor. We recovered 83% of the total Br^- added to the snowpack surface in forest floor lysimeters. In contrast, the forest floor was a fairly strong sink for SO₄^2- and NO₃^-. Respectively, 54% and 49% of the total SO₄^2- and NO₃^- added to the snowpack surface was recovered in forest floor leachates. These results indicate that almost all of the SO₄^2- and NO₃^- that accumulates in the snowpack during winter infiltrates the forest floor, where a significant portion (~50%) is subsequently retained or transformed.