An assessment of the occupational exposure to styrene and associated chemicals in Denmark was carried out by retrieving all measurements from the archives of the Danish National Institute of Occupational Health. A total of 2,528 air samples containing styrene had been collected from 256 workplaces during the years 1955-88 and analyzed by the chemical laboratory at the Institute. The mean for all samples was 265 mg/m3. The concentration decreased from 714 mg/m3 in the early period (1955-70) to 172 mg/m3 in the late period (1981-88). Spraying and unspecified lay-up and production of boats, carriages, and stationary containers were associated with the highest concentration. A total of 34 chemicals were measured. The most frequent co-contaminant to styrene was acetone, which was measured in 2,263 samples with a mean concentration of 131 mg/m3. Dichloromethane was measured in 208 samples with a mean concentration of 51 mg/m3, xylene in 148 samples with a mean concentration of 49 mg/m3, and toluene in 116 samples with a mean concentration of 113 mg/m3. The study was undertaken to analyze historical styrene concentrations in air to aid in the selection of industrial cohorts to be included in epidemiologic studies.