A new method for determination of hydrogen peroxide in atmospheric samples is described. Cryogenically collected H 2 O 2 is reacted with sodium salicylate in the presence of Fe 2 + to produce dihydroxybenzoate, which is separated from the reaction mixture by high performance liquid chromatography and detected by UV absorption. Measurements of atmospheric H 2 O 2 were conducted in Las Vegas, NV from June 1999 to December 1999 to evaluate and characterize the method. Measured mixing ratios of H 2 O 2 (there were also non-detects) ranged from 0.012 to 2.74 ppbv, with expected correlations to primary gaseous pollutants and strong seasonal variation consistent with a photochemically derived species. It was concluded that the method is easy to use and has sufficient sensitivity and selectivity to be useful in atmospheric monitoring.