Ni and Co are trace transition elements which exhibit very low concentrations in continental water. Therefore, due to these very low amounts, little is known about their geochemical cycle. A square-wave voltammetry method, initially developed for seawater, was adapted to fresh water in order to get reliable analysis of these two elements. This method uses an intermediate complexation step with dimethylglyoxime in order to increase the sensitivity of the polarographic analysis and leads to detection limits close to 1 · 10−11M for Co and 3 · 10−10M for Ni. Experiments take place in a clean room and blank tests were carried out to make sure that storage bottles do not alter the sample content. This method was used to determine Ni and Co distributions in the water column during the stratification period and in the sediment pore water of a eutrophic lake. Ni concentration is roughly independent of the water column redox status, and is below detection limit in the sediment pore water. This can be related to the presence of sulfide in these waters. Co concentration strongly increases below the chemocline and its profile is close to that of manganese. Co concentration increases downward in the pore water. Co can be adsorbed onto Fe- and Mn-oxyhydroxides and is released into solution when oxides are dissolved.