Superconductive samples with nominal compositions La3CaxBa3Cu6+xOy (1≤x≤5) were prepared. The best superconductivity with T c (zero) = 80.0 K and ∆Tc = 1.5 K was found in the sample having x = 1; the composition was La3CaBa3Cu7O155+δwhich had a tetragonal tripleperovskite structure with unit cell dimensions a = 3.88A and c = 11.64A. Only one superconducting phase, La3CaBa3Cu7O155+δwas observed in these superconducting samples. Unlike theTl-Ca-Ba-Cu-O or Bi-Ca-Sr-Cu-O oxidesystems, the complexity of the superconductingphase in the La3CaxBa3Cu6+xOy series was not increased for x≥2. The amount of impurities, such as Ca2CuO3, gradually increased with x≥2. Tc of La3CaxBa3Cu6+xOy decreased with decreasing volume of the unit cell of the superconducting phase; this effect probably resulted from the substitution of further Ca atoms at the Ba and La sites.