Obtaining reliable results of exposure to styrene in field studies requires an appropriate methodology not only for analytical methods but also for the main strategy of conducting the surveys. This paper briefly describes how and why analytical methods for styrene in air, for its main metabolites in urine (mandelic and phenylglyoxylic acids) and for critical biological function tests were either chosen from the literature or adapted or developed to fit our criteria of convenience and reliability. In a second step of the preparation of field studies, experimental exposures to styrene were carried out on volunteers so that the best indicators of exposure could be determined and data could be obtained on the elimination kinetics of the urinary metabolites and the quantitative relationships between exposure and the urinary concentrations of mandelic and phenylglyoxylic acids. Finally field investigations, including air and biological monitoring, complete industrial hygiene surveys and medical examinations, have been organized and are being carried out in the Swiss polyester industry. Preliminary results concerning biological monitoring are given.