Distribution coefficients for the sorption of Pb2+, Cu2+, Cd2+ and Zn2+ by peat were determined as a function of the Ca2+-content of peat as well as of the Ca2+-concentration in the solution. The amount of heavy metal ions taken up was measured for Cu2+, Cd2+ and Zn2+ by atomic absorption spectrometry and for Pb2+ by using Pb-212 as a radioactive tracer. The results show that the distribution coefficients of the heavy metal ions increase, if one increases the initial ratio of the Ca2+ H+-ions in the peat phase. The distribution coefficients for the heavy metal ions decrease, however, if - at constant initial Ca2+-content of the peat - the Ca2+-concentration of the solution is increased.