Samples of antimony(III) phosphate, a layered material, were prepared at room temperature, using the two allotropic forms of Sb2O3, layered valentinite and cubic senarmontite. The compounds were characterized by infrared spectroscopy, X-ray diffraction, and thermogravimetric-differential thermal analysis. Solids exposed to ammonia, ethylenediamine, or hydrazine vapors also were studied. The interaction between SbPO4 and the bases always led to the formation of stoichiometric amounts of Sb2O3 and hydrogen phosphate(-2) salts of the bases. With ammonia, the SbPO4 raw materials gave rise to valentinite or senarmontite, depending on which Sb2O3 allotropic form was used to prepare antimony phosphate. This effect was modified when the SbPO4 preparations were preheated at 600 degrees C, in which case, a mixture of both forms was obtained. With ethylenediamine and hydrazine, SbPO4 of whatever origin always gave rise to senarmontite. No evidence of intercalation in the interlayer region of SbPO4 was obtained.