Provides guidelines for the biological monitoring of occupational exposure to four metals (aluminium, arsenic, cobalt, and nickel), three solvents (benzene, methanol, and methylene chloride), two groups of pesticides (dithiocarbamates and pyrethroids), aromatic amines, and polycyclic aromatic hydrocarbons. Guidelines for each chemical follow a common framework. The chemical is first introduced in terms of its physical and chemical properties, possible occupational and non-occupational exposures, data on toxicokinetics and toxic effects, and a comparison of currently available biological indicators of exposure. Recommended biomarkers are then discussed in terms of suggested methods of sampling and analysis, and guidelines for the interpretation of test results.