Mutagenicity of copper sulphate was evaluated in vivo by chromosome aberration, sperm abnormality and micronucleus tests in mice. Dose, route and time influenced significantly the frequency of chromosome aberration, incidence of micronucleus and sperm abnormality. Relative sensitivity of three assays are: sperm abnormality>chromosome aberration>micronuclei formation. The present results revealed the mutagenic property o CuSO₄ in mouse in vivo test system.