This paper describes improved techniques for measuring occupational exposure to benzene vapour, and for assessing the amount of benzene absorbed by the body. “Intrinsically safe” personal air samplers collect benzene vapour on silica gel from which it is eluted and the amount of benzene determined by gas chromatography. Benzene concentrations in the presence of other hydrocarbon vapour can be determined down to about 0·1 ppm over periods from 15 min to 8 hr. To determine the amount of benzene taken into the body, breath sampling tubes have been developed to collect samples of a single breath for transport to a laboratory for gas chromatographic analysis. Additionally, a half-face respirator has been modified to trap, on silica gel, benzene exhaled over 10-min periods. The samples are analysed by the method used for air samples and the sensitivity of both techniques is similar to that of air sampling. Comparison has been made of several techniques for assessing benzene intake by determining the concentration of phenol in urine. A laboratory method has been developed for hydrolysing conjugated phenol and for its specific determination in the presence of cresols. All methods have been tested in field use and have been correlated in a controlled 115 ppm-hr exposure of a single subject. This has confirmed the advantages of exhaled breath sampling as a measure of the long term retention of benzene. The methods have been developed primarily for special industrial hygiene investigations which are being undertaken, but are also suitable for routine monitoring. Further work is required to establish standards for use in controlling occupational exposure to benzene.