There is concern regarding chromium and nickel species in the emissions from incineration of municipal wastewater sludge because of the associated cancer risk. The Environmental Protection Agency's (EPA) Office of Water Regulations and Standards (OWRS) is developing new regulations for sewage sludge incinerators and EPA's Risk Reduction Engineering Laboratory (RREL) has been assisting OWRS in the collection of supporting data. The paper reports new data on emissions of chromium and nickel species and associated emissions needed to respond to public comments. The primary objectives of the portion of the RREL/OWRS research program described in the paper are to determine (1) the ratio of hexavalent chromium to total chromium and (2) the ratio of nickel subsulfide to total nickel in sewage sludge incinerator emissions under several incinerator operating conditions. Secondary objectives include comparing the analytical results for emissions of chromium and nickel subspecies determined by different analytical procedures, and gathering data on other metals and inorganic and organic gaseous components in uncontrolled and controlled incinerator emissions.