Legacy information systems are usually defined from a technical perspective only. However, there is also a business dimension to the legacy information system problem represented by the organisation structure, business processes and procedures that are bound up in the design and operation of the existing IT systems. Legacy information systems have evolved over long periods of time in response to incremental changes in business strategy. Firms are now being forced to change more radically and quickly due to a changing business environment than was the case in the past. Evidence from case study research has shown that the legacy information system problem includes both business and technical dimensions, resulting in misalignment between the strategic vision of the business and the old business model embodied in the legacy. Understanding legacy information systems is necessary when forming new strategies to overcome the legacy problem and to realign IT with the new strategic vision.