The low-cristobalite-type modification of Al_0.5Ga_0.5PO₄ is prepared by annealing the amorphous precipitate of stoichiometric phosphate at 1300°C. The phase purity of the sample is ascertained by powder X-ray diffraction. The crystal structure is refined by Rietveld refinements of the neutron and X-ray diffraction data of the polycrystalline powder. This compound crystallizes in an orthorhombic lattice with unit cell parameters,a=7.0295(8),b=7.0132(8), andc=6.9187(4)Å,V=341.08(6)ų,Z=4 Space group C 222₁, No. 20. The crystal structure analysis reveals the random distribution of the Al3+and Ga³⁺having tetrahedral coordination with typical M–OM=Al³⁺:Ga³⁺ bond lengths as 1.74 Å. Similarly, the P⁵⁺ have tetrahedral coordination with typical P–O bond lengths 1.52–1.54 Å. The MO₄ and PO₄ tetraheda are linked by common corners forming a three-dimensional framework lattice. The details of the crystal structure are presented in this paper