We present a systems modelling approach to evaluating the success of an agroforestry extension program in Leyte the Philippines. During the program, variables which are intrinsic to farmers’ socio-economic and farming systems were found to have influenced the uptake and acceptance of extension advice. Evaluation of the program therefore depended on identifying the variables and their interdependencies and assessing their relative influence on program outputs. For this purpose, a systems approach which encourages breaking systems into component variables, but also acknowledges the context of problems, assisted construction of models. Using both empirical data collected during program activities and input from stakeholders, Bayesian Belief Network (BBN) modelling was undertaken to predict critical success factors for the four main extension activities, namely recruitment, the effectiveness of written extension materials, development of farmers’ self-efficacy in nursery and silvicultural management and attrition of participating farmers. A key predicted constraint to program recruitment is farmers’ perception of harvest security and whereas this variable can be partly addressed through dissemination of information on harvesting legislation, title security cannot. Differing levels of farmers’ education flow through to differences in predicted reading ability, comprehension of extension literature and possible misconstrual of information. The variable most critical to the development of farmers’ self-efficacy is extended problem-solving support
