In 1992, even before a formalized agricultural extension system existed, the Farmer Field School was introduced in Vietnam as a farmer education methodology aiming at enhancing farmers' agroecological knowledge, critical skills and collective action to support sustainable agricultural development. Over the years, the model saw a wide range of applications and adaptations to serve different development needs, while preserving the underlying principles to capacitate, empower and organize farmers. The training experience has proven to be effective and is appreciated by farmers who benefit from learning to gather information, make informed decisions and manage their farms independently in a liberalizing and rapidly changing development climate. Despite convincing impact at the farmer level, the model has not been widely mainstreamed into the agricultural extension system, due to several reasons explored in this paper. Lessons learned should be more thoroughly evaluated and documented to influence future policy-making. (Contains 2 tables and 4 notes.)