Toxic chemicals that persist for a long time in the environment, travel great distances through various media from their point of origin, bio-accumulate in humans and other organisms and are bio-concentrated through food chains are referred to as persistent toxic substances (PTS).PTS are on the priorities of the Contaminant-base Operational Programme of GEF International Waters focal area (OP-10). Building on its historical interests and strengths in the area of chemicals and given its role in the support to the ongoing negotiations for a global POPs convention, UNEP has made a concerted effort to build a coherent portfolio based on strategy paper issued in 1998.