The search for literature data in the ternary systems M2+, Ca2+ + SO42- + H2O (M = Mg, Mn, Co, Ni, Cu, Zn) revealed a lack of data. A reason might be the difficulties of Ca analysis at high concentrated bivalent metal solutions. The solubility of gypsum was determined in MSO4 solutions (M = Mg, Mn, Co, Ni, Cu, Zn) over a broad concentration range at T = 298.15 K and T = 313.15 K. With increasing magnesium and heavy metal sulfate, respectively, the gypsum solubility decreases to a minimum and rises afterward to a maximum at about 1.2 mol MSO4/kg. Above that concentration, the solubility of gypsum decreases again until saturation with MSO4. At both temperatures and in the whole concentration range, no double salt formation was noticed. With increasing temperature, the solubility of gypsum increases also.