Electrophilic compounds are widely used in industry. Plastic and dyeing industries are foremost examples of sites where workers are exposed to electrophilic compounds. Besides their immediate effect on different body systems, electrophilic compounds include most mutagenic and carcinogenic substances. The present study was carried out to elucidate the possibility of using nonselective assays in the biological monitoring of occupational exposure to electrophilic compounds. The study included a total number of 225 workers selected from the Plastic and Battery Company where workers are exposed to styrene (n = 70), and the Kafr El Dawar chemical and Dyeing Company where workers are exposed to aniline (n = 60) and benzidine (n = 25). Workers exposed to diesel engine exhaust were selected from a bus garage in Smoha (n = 70). A comparison group consisting of 141 subjects was selected from the administrative departments of the selected factories. The biochemical tests carried out on each subject included: (1) estimation of the biological indices of exposure: urinary mandelic acid and benzidine, blood methemoglobin, and carboxyhemoglobin, (2) liver and kidney function tests; and (3) nonselective biochemical parameters of early detection of carcinogenic and mutagenic risk: urinary thioether levels, urinary RNase and alpha esterase activities. The study revealed that two out of three nonselective assays have been affected by occupational exposure to electrophilic compounds. These were the urinary thioethers and RNase levels. Their determination is recommended in the biological monitoring of workers exposed to such agents especially in developing countries.