This report compares cancer classification systems, health risk assessment approaches, and procedures used for establishing occupational exposure limits (OELs), in various European countries and scientific organizations. The objectives were to highlight and compare key aspects of these processes and to identify the basis for differences in cancer classifications and OELs between various scientific organizations and countries. Differences in cancer classification exist in part due to differences in the ultimate purpose of classification and to the relative importance of different types of data (i.e., animal vs human data, mechanistic data, and data from benign vs malignant tumors). In general, the groups surveyed tend to agree on classification of chemicals with good evidence of carcinogenicity in humans, and agree less on classification of chemicals with positive evidence in animals and inadequate or limited evidence in humans. Most entities surveyed distinguish between genotoxic and nongenotoxic chemicals when conducting risk assessments. Although the risk assessment approach used for nongenotoxic chemicals is fairly similar among groups, risk assessment approaches for genotoxic carcinogens vary widely. In addition to risk assessment approaches, other factors which can affect OELs include selection of the critical effect, use of health-based vs technology-based exposure limits, and consideration of technological feasibility and socioeconomic factors. © 2001 Academic Press.