The state of the art and challenges in developing in situ voltammetric probes for direct measurements in natural waters are presented. Articles dealing with this topic are reviewed. Use of voltammetric probes in the laboratory and in the field is outlined. An up-to-date account of the results reported in the literature on the development of existing in situ voltammetric systems for such measurements is given. Emphasis is placed on the need for such systems to gain a better understanding of the mechanisms of processes occurring in natural aquatic systems. Suggestions are made for future development.