RATIONALE: Glycol-based antifreeze liquids, commonly composed of ethylene glycol or propylene glycol, have important uses in automotive cooling, but they should be handled with care due to their toxicity, ethylene glycol is highly toxic to humans and animals. A fast, accurate, precise and robust method was developed for simultaneous quantification of 7 most important glycols and their isomers. METHODS: Glycols were analyzed from diluted sample solution of coolants using gas-chromatography coupled with mass spectrometry in single ion monitoring mode. RESULTS: The method was developed and validated for 7 individual glycols (ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol). Limits of detection (1-2 µg/mL) and limit of quantification (10 µg/mL) obtained were appropriate. The present method was applied for determination of glycols in 10 different anti-freeze liquids commercially available on Romanian market, proving to be reliable. CONCLUSIONS: A method that requires only a two-step dilution of anti-freeze samples combined with direct liquid injection GC-MS was validated for the simultaneous quantification of 7 glycols (and their isomers) in 10 different types of anti-freeze liquids. The results obtained in the validation procedure proved that the GC-MS method is sensitive and precise for quantification of glycols.