It is presently well recognized that total concentrations of trace elements in any environmental compartment supply insufficient information to understand important phenomena. The distinction and separate analysis of specific chemical species are essential for understanding cycles in the aquatic environment, involving identification and quantification of sources, transport pathways, distributions and sinks, or, in the area of interactions between trace elements and organisms to understand uptake, distribution, excretion mechanisms and effects. In the past, various ways have been developed to determine the nature and extent of complexation of trace elements in natural systems. Approaches have been followed along very different lines. These have not always been fully appreciated by specialists working in even related fields of complexation research. The first International Symposium on the Complexation of Trace metals in Natural Waters was held at the Netherlands Institute for Sea Research (NIOZ, Texel, the Netherlands from 2-6 May 1983. The scientific programme was planned by the chief organizers Drs. C.J.M. Kramer and J.C. Duinker (NIOZ) together with Prof. Dr. H.W. Nurnberg (Kernforschungsanlage, Julich, Federal Republic of Germany) and Dr. M. Branica (Rudjer Boskovic Institute, Zagreb, Yugoslavia).