A new phase of ZrGeO4 was hydrothermally synthesized from a mixture of ZrOCl2 solution and GeO, powder at 240degreesC. X-ray diffractometry patterns of synthesized ZrGeO4 particles, which had better crystallinity than ZrSiO4 particles prepared by the same process from ZrOCl2 and tetraethoxysilane, could be indexed for a zircon-type tetragonal structure, having a(0) = 0.6694(0) and c(0) = 0.6265(7) nm. The c/a ratio of synthesized ZrGeO4 (0.9360) was larger than that of ZrSiO4 (0.9054). Solid solutions with. zircon-type structure over the whole composition range in the ZrGeO4-ZiSiO(4) System were also directly synthesized through the same solution route. The secondary particle size of zircon-type Zr(Ge,S')O-4 solid solutions decreased, and its morphology gradually changed from octahedron-like to blood-red cell-like with decreased GeO2 content.