Flexibility is assumed to be one of the most important requirements for firms to survive and prosper in turbulent and unpredictable environments. In this article, we first define the concept of flexibility, showing that there are, in fact, several different types of flexibility, e.g., supply, production, and product assortment flexibility. A longitudinal study designed to overcome difficulties encountered in previous empirical studies based on the resource view of strategy found that different, balanced forms of flexibility are required for firms to cope in uncertain, turbulent environments. Finally, the article discusses the theoretical and practical implications of flexibility. (C) 2002 Elsevier Inc. All rights reserved.