Granted that high rates of return usually accompany high market share, it is useful to explore the relationship further. Why is market share profitable? What are the observed differences between low- and high-share businesses? Does the notion vary from industry to industry? And, what does the profitability/market-share relationship imply for strategic planning? In this article we shall attempt to provide partial answers to these questions by presenting evidence on the nature, importance, and implications of the links between market share and profit performance.