Perovskite-related solid solutions, Sr2-xLaxCu1-yTa1+yOz, were synthesized by solid state reaction at 1050-1080 degrees C in air. The crystalline phases were identified by powder X-ray diffraction. Three types of crystal structure were observed including simple cubic perovskite-type, tetragonal perovskite-type and tetragonally distorted (NH4)(3)FeF6-type structure in which Cu2+ and Ta5+ were ordered alternatively. The average valency state of copper in these solid solutions was nearly equal to + 2. The tetragonal phases were observed in a compositional range, z greater than or equal to 5.85, regardless of cation composition. The tetragonality (c/a) for both the perovskite-type and (NH4)(3)FeF6-type phases increased with increasing oxygen content. Ordering between Cu2+ and Ta5+ was not observed in the Sr-rich composition. These facts suggest that oxygen content affects the appearance of the Jahn-Teller effect of Cu2+ leading to the tetragonal distortion and that the cation on the A-site affects the ordering of the cation on the B-site.