This document discusses strategic information systems and how they can provide competitive advantage. It defines strategic information systems as those that support or shape a business unit's competitive strategy by improving processes, products or relationships to gain an edge over competitors. Porter's value chain and five forces models are presented as frameworks to analyze an organization's strategy and how information systems can positively impact different forces like new entrants, supplier/buyer power, and competition. Specific strategies are listed like differentiation, cost leadership and innovation that can be supported by information technology implementations.