Substituted quinolyl and benzothiazolyl hydrazones can be used as metallochromic indicators in the EDTA titration of Cu(II) at pH=6 in 50% ethanol-water media. Common transition elements such as Ag(I), Co(II), Mn(II), Pb(II), Zn(II), Cd(II), Ni(II), Al(III) and Cr(III) interfere with the titration of Cu(II); however, metals which are co-titrated with Cu(II), such as Co(II), Pb(II), Zn(II), Cd(II), and Ni(II), may be titrated individually with EDTA employing a differential technique in which the Cu(II)-hydrazone end point is used. In addition, the properties of the complexes of Cu(II) with the hydrazone indicators have been studied. In 50 % ethanol at pH=6, 1∶1 ligand:Cu(II) complexes are formed which have apparent molar absorptivities in the vicinity of 20 000. As the aldehyde moiety of the hydrazone increases inπ character, a bathochromic shift is observed for the absorbance maxima of the Cu(II)-hydrazone chelates.