1-Methoxy-2-propanol (M2P) is finding increasing industrial use as a less toxic alternative to the short-chained ethylene glycol ethers. Like most glycol ethers, M2P is readily absorbed through the skin and biological monitoring is therefore appropriate in assessing occupational exposure. An analytical method, suitable for routine monitoring, was developed for the determination of free M2P in urine. The method involves solvent extraction, gas chromatography-mass spectrometry and is sensitive (detection limit 1 mumol/l), specific and reproducible (intra- and inter-assay coefficients of variation 5% and 9%, respectively). A human volunteer study, involving six volunteers, was also conducted. Volunteers were exposed to 100 ppm M2P for 8 h (the occupational exposure standard in the UK) including a 30-min break. Post-exposure levels of free M2P in urine were found to reach up to 110 mumol/l). Levels of M2P were also monitored in blood (maximum 103 mumol/l) and exhaled air samples (up to 252 nmol/l). The volunteer study showed that M2P is rapidly excreted in urine with a half-life of less than 2.6 h.