INTRODUCTION Large quantities of carbonyl compounds are used worldwide as raw materials and intermediates in the chemical and plastics manufacturing industries. These compounds are eye, skin, and respiratory system irritants and many have also been identified as animal teratogens,mutagens, and carcinogens. Because of their widespread,high-volume industrial usage they are present in work- place air spaces and industrial waste materials. They are also present in dump site leachates, which can contami-nate ground water that may eventually be used fordrinking water. This application note describes a method wherein carbonyl compounds in aqueous samples or extracts are first derivatized with dinitrophenylhydrazine (DNPH).After derivatization, the carbonyl compounds are extracted and injected onto a C18, reversed-phase high- performance liquid chromatography (RP-HPLC) column and separated using gradient elution. The separated compounds are then quantified by UV detection at 360 nm. These analytical procedures are patterned after and consistent with U.S. EPA Method 554, which specifically addresses drinking water samples. It is also consistent with U.S. EPA Method 8315, which addresses aqueous and solid waste, soil, stack gas, and indoor air samples.