For occupational toxicants of current relevance, the documentations for the established MAK values are provided. These include an authoritative review of the available toxicological studies and data. For every substance, toxic effects, mechanisms and modes of action, toxicogenetics and metabolism, effects in man and animals are described. The carcinogenic, germ-cell mutagenic, sensitizing or skin-resorptive effects as well as their toxicity to the reproductive system are evaluated. Basic physico-chemical data are provided as well. The documentations are thus not only essential for the application of MAK values but provide a concise toxicological overview for each substance.