HUO2PO4•4H2O (HUP) forms a laminar intercalate with butylamine,c = 29.30(5) Å, which accepts cationic metals in exchange for then-butylammonium ions. Hydrated uranyl metal phosphates M(UO2PO4)2•nH2O (M = Mn, Co, Ni, Cu, Zn, Cd) are obtained by ionic exchange and were studied by thermal analysis and X-ray diffraction. The tetragonal structures of all these product compounds are derived from HUP. The diffuse electronic reflectance spectra of every sample show characteristicabsorption bands. In the spectra of the Co, Ni, and Cu phosphates there are other bands in the 500–800 nm zone compatible with their observed aquocation transitions.