Agricultural extension services are crucial for the rapid spread of research results to farmers and for transmitting information about farmers’ needs, circumstances, and problems to researchers. In developing countries, public extension organizations are dominant. These public extension systems are often inadequately funded, have high costs, and their effectiveness is limited by many administrative and design deficiencies and challenges. Chief among these are the large scale and complexity of extension operations, the weak links between extension and research, problems of accountability, weak political commitment and support, weak management systems, severe difficulties of fiscal unsustainability, and difficulties of tracing extension impact. Disenchantment with the traditional, public extension programmes has led to the emergence of other approaches aimed at overcoming some of the weaknesses inherent in the public extension systems. This paper reviews the challenges of decentralized, farmer-led and fee-for-service extension.