Introduction Bjørn Lomborg; Part I. The Challenges: 1. Air pollution Bjørn Larsen, Guy Hutton and Neha Khanna; 1.1. Alternative perspective Jitendra Shah; 2. Conflicts – the security challenges in conflict prone countries Paul Collier, Lisa Chauvet and Haavard Hegre; 2.1. Alternative perspective Ibrahim A. Elbadawi; 2.2. Alternative perspective Andrew Mack; 3. Diseases – disease control Dean T. Jamison, Prabhat Jha and David Bloom; 3.1. Alternative perspective David Canning; 3.2. Alternative perspective Ramanan Laxminarayan; 4. Education Peter F. Orazem, Paul Glewwe and Harry Patrinos; 4.1. Alternative perspective Victor Lavy; 4.2. Alternative perspective Lant Pritchett; 5. Global warming Gary W. Yohe, Richard G. Richels, Richard S. J. Tol and Geoffrey J. Blanford; 5.1. Alternative perspective Chris Green; 5.2. Alternative perspective Anil Markandya; 6. Malnutrition and hunger Sue Horton, Harald Alderman and Juan A. Rivera; 6.1. Alternative perspective Reynaldo Martorell; 6.2. Alternative perspective Anil B. Deolalikar; 7. Sanitation and water Dale Whittington, W. Michael Hannemann, Claudia Sadoff and Marc Jeuland; 7.1. Alternative perspective Jenna Davis; 7.2. Alternative perspective Frank Rijsberman and Alix Peterson Zwane; 8. Subsidies and trade barriers Kym Anderson and L. Alan Winters; 8.1. Alternative perspective Alan V. Deardorff; 8.2. Alternative perspective Anthony J. Venables; 9. Terrorism Todd Sandler, Daniel G. Arce and Walter Enders; 9.1. Alternative perspective S. Brock Blomberg; 9.2. Alternative perspective Michael D. Intriligator; 10. Women and development Elizabeth M. King, Stephan Klasen and Maria Porter; 10.1. Alternative perspective Lawrence Haddad; 10.2. Alternative perspective Aysit Tansel; Part II. Ranking the Opportunities: Jagdish Bhagwati, François Bourguigno, Finn E. Kydland, Robert Mundell, Douglass North, Thomas Schelling, Vernon L. Smith and Nancy Stokey; Expert panel.