The concentration range for nitrite (NO2-) in 115 rain samples collected in Wilmington, NC, from June 1996 through February 1998 was 0.022−0.603 μM. Nitrite concentrations did not correlate with precipitation volume, suggesting a continuous supply of nitrite during rain events possibly by slow scavenging of gas-phase material such as HONO(g) or NO2(g) or in-cloud oxidation of other reduced forms of nitrogen. Nitrite levels exhibited no seasonal oscillations, which is in contrast to other rainwater parameters at this site such as pH, nitrate, non-seasalt sulfate (NSS) and ammonium. Concentrations of nitrite did not correlate with concentrations of pollutant indicators (pH, nitrate, and NSS). The concentration of nitrite in both winter El Nino rains and summer tropical rains was less than half its concentration in non-El Nino or non-tropical events, suggesting a possible terrestrial source of nitrite or nitrite precursor. Controlled laboratory studies demonstrated that hydrogen peroxide can oxidize nitrite in rainwater at environmentally relevant H+, H2O2, and NO2- concentra tions. Nitrite oxidation by H2O2 in the aqueous phase has important ramifications with respect to N cycling and acid generation within the troposphere.