Solid solutions in the series (BaxPb1-x)(Mg1/3Nb2/3)O3 which belong to ABO3 type compounds were studied using the X-ray Rietveld technique. The compositions corresponding to Ba = 0.2 and 0.4 have the same structure as that for Ba = 0 (pm3m). The composition corresponding to Ba = 0.6, 0.8 and 1.0 show ordering at the B-site. The structure of these compounds is solved in the space group P3̄m1. The temperature factor of Pb atom in Pb(Mg1/3Nb2/3)O3 is very high. The temperature factor of Ph/Ba reduces with Ba substitution. The octahedral distortions are small for the compositions in this series. There is an increase in Nb-O bond length with the substitutions of Pb.