Hydrogen peroxide (H₂O₂) and organic hydroperoxides (ROOH) are species that contribute to the total oxidizing capacity of the atmosphere and are indicative of the extent of free radical chemistry involved at a particular location. With increased understanding of atmospheric oxidation chemistry, the importance of the role of H₂O₂ and ROOH in redistributing free radicals, the driving force of atmospheric chemistry, is being realized. In view of this, the results of laboratory, field, and modeling investigations have been combined in this paper to provide a comprehensive review of the tropospheric chemistry of H₂O₂ and ROOH. The article has reviewed the current understanding of tropospheric gas phase and aqueous phase peroxide chemistry, encompassing formation mechanisms and chemical and physical removal processes. The spatial and temporal variation in peroxide concentrations, as shown through both field measurements and model predictions is also discussed. Historically preserved records in polar ice cores have revealed an increase in peroxide concentration extending back to the Last Glacial Maximum. Although these records are not yet a direct measure of atmospheric peroxide concentration at the time of snow deposition, they add to the evidence of global climate change and reinforce the need for the continued development of modeling studies, aimed at predicting the future oxidizing capacity of the atmosphere. These models can be developed by improved understanding of atmospheric peroxide chemistry.