In August 1999, the Twelfth Workshop on Languages and Compilers for P- allel Computing (LCPC) was hosted by the Hierarchical Tiling Research group from the Computer Science and Engineering Department at the University of California San Diego (UCSD). The workshop is an annual international forum for leading research groups to present their current research activities and the latest results. It has also been a place for researchers and practitioners to - teract closely and exchange ideas about future directions. Among the topics of interest to the workshop are language features, code generation, debugging, - timization, communication and distributed shared memory libraries, distributed object systems, resource management systems, integration of compiler and r- time systems, irregular and dynamic applications, and performance evaluation. In 1999, the workshop was held at the International Relations/Paci c Studies Auditorium and the San Diego Supercomputer Center at UCSD. Seventy-seven researchers from Australia, England, France, Germany, Korea, Spain, and the United States attended the workshop, an increase of over 50% from 1998.