This paper provides a model for aligning business and information technology strategies. The model, expanded from the earlier study by Henderson and Venkatraman, is composed of four elements: business strategy, business infrastructure, information technology strategy, and information technology infrastructure, and suggests different ways of aligning business and information technology strategies. Basically, there are three types of aligning: integrating, domain based aligning, business reengineering. The validity of the model is supported by case studies.