Solar-light reaching the earth surface is able to induce chemical reactions in absorbing chemicals. For many organic pollutants dispersed in surface waters, photolysis is an important transformation process. It results from absorption of light by the chemical itself or it is mediated by sensitizing or photoinducing chromophores contained in surface waters. Coloured dissolved organic matter (cDOM) and nitrate ions are among these. This paper gives a brief description of major photochemical processes that may occur in surface waters. It is illustrated by three examples of light induced pollutant transformation. The high volume chemical I-naphthol and the herbicides methabenzthiazuron and mesotrione were chosen as substrates. Analytical and kinetic aspects of the reactions are reported. (C) 2007 Elsevier B.V. All rights reserved.