This paper critically assesses the standard IMF analytical framework for debt sustainability in emerging markets. It focuses on complementarities and trade-offs between fiscal and external sustainability, and interactions and feedbacks among policy and endogenous variables affecting debt ratios. It examines current fragilities in emerging markets and notes that domestic debt is of concern. Despite favourable conditions, many governments are unable to generate a large enough primary surplus to stabilize public debt ratios. Worsening global financial conditions may create difficulties for budgetary transfers, posing greater challenges to government debt management since restructuring often is more difficult for domestic than external debt. Debt sustainability: Concept, analysis and limitations -- The IMF approach to debt sustainability -- Conclusions -- Annex : Fiscal and External Sustainability.