The environmental behaviours of the heavier halogenated hydrocarbons such as DDT and its residues and the polychlorinated biphenyls are known in general form. One unexpected aspect involved their atmospheric transport in the vapour phase about the Earth. Although the production and use of these compounds has been restricted in some northern hemispheric nations, there appears to be a continuing steady use of DDT in the world as a whole, but with a decided shift southwards. As a consequence of their alleged impacts upon living systems, of their continued movements about the surface of the Earth, of their persistance in the environment and of their high rates of production, there is still a continuing need to study these compounds and other synthetic organic halogenated hydrocarbons in our surroundings and their involvements with life processes.