A series of BaxSr1-x(NO3)(2) crystals have been grown from aqueous solutions with different initial Ba2+/Sr2+ ratios. These crystals were characterized by powder X-ray diffraction. All diffraction data were well indexed according to the simple cubic structure, and the variation of lattice constants with the concentration of Ba2+ in the crystals accorded quite well to Vegard's Law. The composition of the Sr(NO3)(2) crystal doped with Ba2+ was studied with an electron microprobe. It was found that Ba2+ was enriched in the 100 sectors. The quality of the crystals with different composition. estimated by the high-resolution X-ray diffraction indicated that the second cation added to the crystalline phase degrades the crystalline quality of the crystals. Equilibrium behavior in the Ba(NO3)(2)-Sr(NO3)(2)-H2O system was analyzed using Lippmann's phase diagram, and the equilibrium distribution coefficient D-Ba = 769.2. This large value of D indicates that the Ba2+ ion is drastically preferentially partitioned towards the solid phase.