Titanium(III) and copper(II) salts of various dialkyl phosphoric acids have been prepared. Molecular weight measurements on the copper(II) dialkyl phosphates show that they are monomeric in ethanol but aggregate to dimeric forms in chloroform, and to trimeric and tetrameric forms in dichloro- methane, while copper(II) di(2- ethylhexyl) phosphate reaches a molecular weight corresponding to a pentamer in n-hexane. Magnetic susceptibility measurements indicate the absence of strong exchange coupling in the copper(II) dialkyl phosphates. E.s.r. measurements have been made on the titanium(III) dialkyl phosphates doped into the corresponding indium(III) dialkyl phosphates. Similar measurements have been made on the copper(II) dialkyl phosphates doped into the corresponding cadmium dialkyl phosphates. E.s.r. measurements have been carried out on chloroform and dimethylformamide solutions of the copper(II) dialkyl phosphates and the triplet state spectra observed at 77 K used to extract the magnetic and structural parameters associated with the dimeric forms of the copper(II) dialkyl phosphates. Infrared spectral measurements have been made on the titanium(III), indium(III), copper(II) and cadmium(II) dialkyl phosphates and the major peaks assigned.