Foundations; 1. Special and differential treatment in the WTO; 2. The rationale for South-South services trade; 3. The quest of this study; Part I. Preferential Services Trade: 4. History and geography of preferential services trade; 5. Stock-taking of preferential services trade agreements; 6. The current level of liberalisation; 7. The special case of South-South preferential services trade; Part II. Legal Regime for Preferential Services Trade: 8. Historical background of preferentialism in services trade and its regulation; 9. GATS Art. V; 10. Regulatory flexibilities in the GATS: special and differential treatment; 11. Compliance with GATS worldwide; 12. Loopholes in the GATS: problems in practice; 13. Innovation in South-South agreements?; 14. In summary; Part III. Legal Regime for South-South Preferential Services Trade: 15. The legal scope of flexibilities for South-South preferential services trade; 16. Legal arguments for a large scope of flexibilities in the GATS; 17. New approach to a better use of the scope of flexibilities; 18. Systemic considerations; 19. In summary; Part IV. Conclusions: 20. Lessons for the WTO; 21. Lessons for the architecture of international economic law; 22. Critical issues for future research.