Pr4V5Si4O22, a new praseodymium vanadium oxosilicate with chevkinite structure, has been prepared by heating PrOCL/V2O5/NH4Cl in an evacuated silica tube; the source of silicon is the reaction tube. It crystallizes in the monoclinic space group C2/m(No. 12) with cell dimensions a= 13.410(2), b= 5.5998(9), c= 11.027(3) Å, β = 100.57(2)°, V= 814.0(5) Å3, and Z= 2, Dcalc= 5.23 g/cm3. The structure consists of PrO8bicapped trigonal prisms, VO6octahedra, and Si2O7pyrosilicate groups. This compound has vanadium oxide layers which are similar to the rutile structure; the V-V distances across the shared octahedral edges are 2.7999 Å and vanadium ions are reduced to show average valence of +3.2.