ith the advent of parallel computer systems, parallel database systems have rapidly become an attractive research area in recent years. A number of parallel database projects have been started in academia and industry, and issues ranging from architecture to algorithms are being investigated. This paper is the first one of the two series papers that survey the research area of parallel database systems. In the paper, the current research directions of parallel database systems are surveyed, and physical design methods for parallel databases and parallelization techniques for query processing are reviewed as well.