The Turkana silvo-pastoral system is a traditional natural resource management strategy for dry lands that forms a sensible basis for improvement. Involvement of the local people is vital in adapting and improving the system, to bring out the potentials that exist in terms of broad land management strategies and more specifically in terms of individual tree species. The participatory extension process being used by the forestry department is presented. It relates to the traditional natural management base as a means of trying to identify potentials, constraints, problems and solutions. Such extension programmes are difficult to evaluate. The data gathering methods for evaluating such extension work, involving over 6000 people, is discussed in the light of a mobile people, lack of sampling frame and large distances in an arid and semi-arid environment. The results of two surveys, together with other informal data gathering mechanisms, show that change is taking place, particularly in qualitative terms, and indicates the effectiveness of the participatory extension programme.