A new high-temperature superconducting compound system, Ba2Can-1CunOx [02(n-1) n-Ba] interstitially doped with calcium or(Ca,Cu) has been identified to exhibit a transition temperature up to 126 kelvin, the highest for a superconductor without a volatile toxic element. 02(n-1)n-Ba has body-centered tetragonal symmetry and an unusual charge-reservoir block. The compounds offer interesting opportunities for high-temperature superconductivity science and technology.