In Vietnam, agricultural extension has contributed to rural development and poverty alleviation over the past two decades of agricultural decollectivization, but it was not very effective in reducing disparities within farmer communities. The study examined how better interactions of extension services with other agencies and information sources may help marginal farmers in catching up with the general improvement of living conditions in a mountainous area in northern Vietnam. It combined three complementary viewpoints on this issue: that of the agricultural extension staff, that of farmers and that of development experts with a long working experience in the mountains of Vietnam. The analysis of existing structures and functions of the extension system revealed a number of obstacles to the participation of marginal farmers in extension programmes and helped to identify relevant domains of intervention. (Contains 7 tables.)