Urea additive compds. with superphosphate pulp components (Ca(H2PO4)(2)center dot H2O and CaSO4 center dot nH(2)O, where n = 0-2), were prepd. The exps. were carried out (i) by milling urea with a dry superphosphate fertilizer in a lab. mortar grinder or (ii) by urea addn. to the reactor after phosphate rock decompn. with H2SO4 or H3PO4. The phase compn. of products was studied by X-ray powder diffraction method. Ca(H2PO4)(2)center dot H2O was more reactive than CaSO4 center dot 2H(2)O and CaSO4 center dot 0.5H(2)O in the urea complexation. The reactivity of anhyd. CaSO4 towards urea was not obsd. in any expt.