The interaction of a number of oxides (fluorides) of bi- or trivalent metals with caesium phosphate's melts is investigated. The main trends in crystallization depending on the Cs/P ratio in a starting melt are discussed. The crystallization fields of <$E roman {CsM sup III P sub 2 O sub 7}> (<$E roman M sup III> - Cr, Fe, In, Lu, Tb), <$E roman {M sup III PO sub 4}> (<$E roman M sup III> - Sm, La, Bi), <$E roman {Cs sub 2 M sub 2 sup II P sub 6 O sub 18}> (<$E roman M sup II> - Mg, Ni), Ni2P2O7, Ni3(PO4)2, and CsZnPO4 are defined. The obtained compounds have been characterized by the powder X-ray diffraction and FTIR-spectroscopy.