Scalable parallel systems are increasingly being used today to address existing and emerging application areas that require performance levels significantly beyond what symmetric multiprocessors are capable of providing. These areas include traditional technical computing applications, commercial computing applications such as decision support and transaction processing, and emerging areas such as “grand challenge” applications, digital libraries, and video production and distribution. The IBM SP2™ is a general-purpose scalable parallel system designed to address a wide range of these applications. This paper gives an overview of the architecture and structure of SP2, discusses the rationale for the significant system design decisions that were made, indicates the extent to which key objectives were met, and identifies future system challenges and advanced technology development areas.