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 µg m−3 and vertical gradients from 1 to 9 ng m−3 / m. The ammonia probability distribution indicates an average concentration of 0.8 µg m−3, although concentrations in excess of 2 µg m−3 are observed. Aerosol measurements indicate ammonium is largely confined to the accumulation mode (0.1 < Dp < 1.0 µm) with a mean concentration of 1 µg m−3. Nitrate exhibits a bi-modal distribution (with mass in both the accumulation and coarse (Dp > 1.0 µm) modes), and is present at mean concentrations of 1.2 µg 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.