This paper presents observations of ammonia, nitric acid and size segregated chemically speciated aerosols above the canopy of a secondary successional deciduous forest in Indiana during spring. Average nitric acid concentrations range between 0.1--1 &mgr;g m-3 and vertical gradients from 1 to 9 ng m-3/m. The ammonia probability distribution indicates an average concentration of 0.8 &mgr;g m-3, although concentrations in excess of 2 &mgr;g m-3 are observed. Aerosol measurements indicate ammonium is largely confined to the accumulation mode (0.11.0 &mgr;m) modes), and is present at mean concentrations of 1.2 &mgr;g m-3. Average dry deposition fluxes calculated from these measurements are: Nitric acid=0.38 mg-N m-2 dy-1, ammonia=1.07 mg-N m-2 dy-1, aerosol-nitrate=0.27 mg-N m-2 dy-1, aerosol-ammonium=0.25 mg-N m-2 dy-1. The total dry deposition nitrogen flux of over 1.9 mg-N m-2 dy-1 is approximately equal to the flux in precipitation as measured at NADP sites in the region. ¿ 1999 American Geophysical Union