The article describes problems of organic substances that have persistent, bioaccumulative, and toxic characteristics likely to cause adverse human health or environmental effects. They are called PBTs (Persistent, Bioaccumulative, Toxic substances) and briefly the state of the PBTs problems in the countries of Central and Eastern Europe is described. As an example of research activities in the region, the long-term research program of Czech and other scientists so-called Project TOCOEN (Toxic Organic COmpounds in the ENviron-ment) is described.