Summaries The paper presents an overview of the historical evolution of BOP support aid in Japan, including changes in its policies and modalities. Organizational set‐up and evaluation methodologies of official donor agencies such as the Ministry of Foreign Affairs, OECF and EXIM are explained. The methodologies are analyzed in the following two ways: items covered in the evaluations and analytical methods. Lessons and suggestions from their evaluations are as follows: objectives of structural adjustment programmes should be clearly defined; direct indicators for impact should be selected in correspondence with policy measures categorized; and the impact of other factors than structural adjustment, especially project aid, should be separated.