This Technical Report is focused on the presence of nitro- and oxy-PAHs in ambient air. It describes how nitro- and oxy-PAH are formed, what typical concentrations are found, what is known about their toxicity, and what sampling and measurement techniques are available. The conclusions of this report are that nitro- and oxy-PAHs concentrations are present in the atmosphere in levels that are of concern regarding their high toxicity. Information on the presence of these compounds in ambient air is as relevant as information about PAHs. Validated techniques for the measurement of nitro- and oxy-PAHs are available.