A review was presented of biological and exogenous factors that may influence the concentration of formate in urine, thus affecting possible use of this metabolite to monitor formaldehyde (50000) exposure. Formate was normally found in the urine of healthy individuals, but exposure to several common industrial compounds, such as formaldehyde, methanol (67561), and acetone (67641), could increase the amounts of formate in the body. Sources of formate and its elimination were reviewed. Several drugs owed their activity to the release of formaldehyde or were deactivated metabolically through demethylation reactions. Dietary and personal factors affecting formate elimination included high intakes of carbohydrate or protein rich food. Ethyl-formate occurred naturally in many fruits and alcoholic beverages. The ethanol of alcoholic beverages could elevate serum formate concentration after consumption. Formaldehyde was found in cigarette smoke. The rate of biotransformation and elimination kinetics of sodium-formate (141537) and its derivatives were understood only marginally. Elevated urinary concentration of formate was a short term outcome of exposure, but the metabolic utilization of excess formate was poorly understood. The author concludes that urinary formate measurement may be useful for assessing worker exposure to formaldehyde or other chemicals, but that interpretation would be difficult due to the many unresolved influences on results. The author recommends that investigations into the primary cause of fluctuations in urine formate concentration be performed, and that controlled laboratory studies be performed on the elimination of formate in persons exposed to chemicals that could be metabolized to formate.