The Twelfth International Workshop on Ceramic Breeder Blanket Interactions was held - under the auspices of the International Energy Agreement for Nuclear Technology of Fusion Reactors (IEA-NFT) and Fusions Materials (IEA-FM) . in Karlsruhe, Germany on September 16-17, 2004 as a short form workshop. The workshop was attended by 19 Participants. The CBBI-12 has provided a forum of specialists involved in the design, research, development and testing of materials and components for lithium ceramic based breeding blankets. The workshop was divided into 5 technical sessions that addressed the general topics of (1) progress in the design of ceramic breeder reactors, (2) breeder material properties, (3) thermal and mechanical behaviour of pebble beds, (4) progress in ceramic breeder material development, and (5) irradiation testing. The 15 presentation, which were given and discussed, are published in these Proceedings. The workshop was hosted by the Institute of Reactor Safety (IRS) at the Forschungszentrum Karlsruhe (Karlsruhe Research Center).