Glycol ethers are known to produce embryotoxic and teratogenic effects in a variety of animal species. In addition, testicular edema and tubular atrophy have been reported. The health effects of this class of compounds are not known in humans, despite the fact that these solvents are widely used in industry. In order to evaluate potential effects in humans, it is first necessary to estimate exposure in the workplace (environmental monitoring). However, in the case of glycol ethers traditional air monitoring may be ineffective because of the low volatility of these solvents and the possible significant exposure via the skin. Biological monitoring can be used to estimate glycol ether uptake by all routes of exposure. The compounds can be measured in blood or their metabolites quantitated in urine. These procedures are suggested for measuring 2-methoxyethanol, 2-ethoxyethanol and 2-butoxyethanol in blood. In addition, tentative procedures have been developed to measure the oxidized acidic metabolites, methoxyacetic acid and ethoxyacetic acid in urine as possible indices of exposure. All procedures have detection limits of less than 11 parts per million. These procedures are ready to be validated in workers exposed to these solvents.