Two decades of the environmental history of dioxins, i.e. of PCCDs and PCDFs, are examined, with the main emphasis being placed on developments in Germany. After a brief consideration of the important, environmentally relevant properties of dioxins, interest is focussed on the course of the Seveso incident of 1976. The environmental effects of dioxins observed in Seveso received global publicity. In the following years our knowledge of the analysis and toxicology of this group of substances greatly improved and the production of dioxins in the aromatics sector of the chemical industry was drastically reduced. In the 1980s, discussions concentrated on the formation of dioxins in waste incineration. The results obtained during this period led to the present situation in which waste incineration is no longer a significant source of dioxin emission in Germany. The greatest known source of dioxins in Germany is in the metallurgical industry. By the year 2000 this dioxin source will also have been largely eliminated.