Biological monitoring of occupational exposure to benzene has been conducted in the petroleum, steel and chemical industries. The urinary benzene-specific biomarker, S-phenylmercapturic acid (PMA), was quantified in post-shift samples using a sensitive enzyme-linked immunosorbent assay (ELISA) and expressed as a function of urinary creatinine concentration. The assay, based on a PMA-specific antiserum, is sufficiently sensitive to measure PMA levels in non-occupationally exposed control subjects. The assay delivers batch results in a timely manner which may be as short as 3 h. Samples were analysed from groups of workers engaged in coke oven combustion processes, petroleum refining and decontamination of a benzene land spill. The construction of a database of results provides an index of benzene uptake as a consequence of the respective work processes and tasks and readily enables benchmarking exercises aimed at comparing degrees of exposure across segments of industry.