This volume constitutes the proceedings of the 12th British National Conference on Databases (BNCOD-12), held at Surrey, Guildford in July 1994. The BNCOD conferences are thought as a platform for exchange between theoreticians and practitioners, where researchers from academia and industry meet professionals interested in advanced database applications. The 13 refereed papers presented in the proceedings were selected from 47 submissions; they are organized in chapters on temporal databases, formal approaches, parallel databases, object-oriented databases, and distributed databases. In addition there are two invited presentations: "Managing open systems now that the "Glashouse" has gone" by R. Baker and "Knowledge reuse through networks of large KBs" by P.M.D. Gray.