A group of workers who were employed at a pharmaceutical manufacturing company and who participated in the entire production cycle were studied. Numerous substances, including iodo-chloro-oxyquinoline, erythromycin, disinfectants, small amounts of cortisones, and preserving agents (prevan and parabenzoates), were used in the manufacturing processes. A control group comprised individuals who were not exposed to hepatotoxic substances. This investigation was designed to determine the risk of hepatotoxicity in the pharmaceutical industry, and a protocol was used that allowed for ease of screening. In the presence of a physician, all subjects completed a clinical history questionnaire. They all underwent a general clinical examination, and specific blood chemistry tests were performed. Certain liver indices that were correlated with cytotoxicity were significantly higher in the pharmaceutical workers than among the controls. The findings confirmed that there was a problem of hepatic involvement among workers in this sector, indicating that the clinical-biohumoral screening protocol used in this study was valid for identifying subjects at risk of hepatotoxicity.