Why do good teams fail? Very often, argue Deborah Ancona and Henrik Bresman, it is because they are looking inward instead of outward.Current traditional, internally focused models of teams aren't working in an increasingly complex and ever-changing world. We need new structures, a new way of organizing, to operate in that world. The authors introduce the X-team, a new, externally focused team model that enables a team to adapt to external change, coordinate with other groups, link to the strategic direction of the firm, and allocate work and leadership across multiple individuals.Based on 25 years of research examining many different kinds of teams -- consulting teams, product development teams, sales teams, and oil exploration teams -- across many industries, Ancona and Bresman make a powerful argument that traditional team models are falling short, and that what's needed, and what is successful, is a new brand of team that emphasizes external outreach to stakeholders, extensive ties, expandable tiers, and flexible membership.The authors show that X-teams not only are able to adapt in a way that traditional teams aren't, but that they actually improve an organization's ability to produce creative ideas and execute them -- increasing the entrepreneurial and innovative capacity within the firm. The new environment demands what the authors call "distributed leadership," and the book highlights how X-teams actually embody this idea.With examples from Microsoft, HP, BP, Merrill Lynch, and many other companies and contexts, the authors will show that X-teams are the key to operating successfully in a world where adaptability is paramount, and that organizations that use X-teams will be moresuccessful than those who rely on traditional teams.