The authors evaluate the impact of farmer field schools, an intensive participatory training program emphasizing integrated pest management. Their evaluation focuses on whether participation in the program has improved yields and reduced pesticide use among graduates and their neighbors who may have gained knowledge from graduates through informal communications. The authors use panel data covering the period 1991-99 in Indonesia. Their analysis, employing a modified "difference-in-differences" model, indicates that the program did not have significant effects on the performance of graduates and their neighbors. The authors discuss several plausible explanations for this outcome and suggest recommendations for improvements.