Sumnutry:The increasing loading of raw water for t,he drinking \ra,t,er supply with trace subst,ances results in an increasing exposure of the population to toxicologirally suspect, substances. At present, the qualit'y of such raw waters is evaluated mainly by cumulative pa,ranieters or individual subst,ances wibh low eco-or hnmantoxicologirnl relevan-e. Xow. about 5 . 10" eiivironment-relevant organic substances must, be taken into account, the number of individual compounds for a loa,ded receiving water being estimated to be 103. Secondary cont'ariiiiiat'ions are caused by oxidative processes of water treatment. I n the trare siibstmce analysis so far only about 40 "jo of the organic subst,ances are isolable by comparatively simple methods. From t,his derives the demand for developing st~andardizecl methods for det,erniining cuinulat~ive and group parameters with a high ~a l u e of information and indication, a8 e. g. organically bonded chlorine or halogens.