This paper uses cointegration analysis to study the competitive interaction among firms within the integrated and minimill groups in the Japanese steel industry. The use of cointegration analysis overcomes some of the limitations associated with prior attempts at modeling firm behavior within groups, and allows us to model strategies that take considerable time to adjust. Results indicate that several strategies displayed slow adjustment characteristics. All of the strategies that displayed these properties were cointegrated within the group. Finally, over the long run, the rate of strategic response to 'shocks' in the system varied across members and strategies: some converged, while others diverged from the group relationship. We conclude by discussing the relevance of our findings to research on strategic groups and competitive dynamics among firms. Thus the paper contributes to the literature on strategic groups and competitive dynamics, and illustrates the use of cointegration analyses to study the competitive behavior of firms. Copyright (C) 2002 John Wiley Sons, Ltd.