Historically, information systems have focused on capturing, storing, managing, and reporting explicit knowledge. Organizations today recognize the need to integrate both explicit and tacit knowledge in formal information systems. Knowledge management continues to be a critical strategy for an organization to achieve a sustainable competitive advantage, and consequently succeed in today's knowledge-based economy. Knowledge management systems (KMS) are a class of information systems that manage, store and distribute knowledge. Knowledge management systems have proliferated in practice. In turn, theoretical research on knowledge management and knowledge management systems has proliferated. Knowledge management systems have emerged as powerful sources of competitive advantage. In this paper, we describe the characteristics and concepts of knowledge management systems. We explain how these systems transform modern organizations to high levels of success and present two successful cases that demonstrate this principal. We conclude with a summary of success factors that were common within two successful knowledge management system implementations.