Styrene and styrene oxide concentrations were measured during the lamination process in the reinforced plastics industry. The mean concentration of styrene in the personal samples was 130 ppm, the highest value measured being 350 ppm. The average concentration for styrene oxide alone was 0.1 ppm, whereas the corresponding measurement for styrene oxide and its decomposition products combined was 0.7 ppm. In comparison then, the concentrations of styrene oxide and its derivatives were much lower (about 0.5% of the total) than those of styrene.