This study was commissioned by the Australian Centre for International Agricultural Research (ACIAR) to evaluate the economic impact of two projects (8201 and 8567) for which ACIAR provided support from 1982–89. These projects were aimed at the improvement of the grain yield potential of pigeonpea (Cajanus cajan) using modern plant breeding, along with associated physiological, agronomic, processing and socioeconomic research. The commissioned organisation in Australia was the University of Queensland. The partners were: Fiji (Ministry of Primary Industries, Native Land Development Corporation); Indonesia (Central Research Institute for Food Crops, Agency for Agricultural Research and Development); India (Indian Council for Agricultural Research, International Crops Research Institute for the Semi-Arid Tropics); and Thailand (Field Crops Research Institute, Department of Agriculture, Kasetsart University, Prince of Songkla University, Chiang Mai University). The initial project was the first formal ACIAR collaborative research project. It aimed to (i) develop widely adapted short-season pigeonpea (SSPP) to replace the traditional longer-season cultivars and (ii) to design management strategies which allowed their full grain yield potential to be realised and demonstrated. Prior to the ACIAR projects the University of Queensland team was targeting their research on these technology options primarily for Australia. The ACIAR projects broadened the scientific and geographic scope of the work to the above four developing countries. The primary focus of this evaluation is on India, where around 90 per cent of the world’s pigeonpeas are grown and where adoption of the SSPP technology options has been both significant and partially documented. There has been limited impact in the other three developing countries and Australia. Brennan and Bantilan (1998) have recently analysed the economic impact of research undertaken by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) on SSPP on Australia and concluded that it is also very limited. Neither of the two ACIAR projects which are the subject of the present evaluation were included in the review of 71 ACIAR projects by Auld (1990) nor the recent assessment by Mauldon (1998). The time and resources for the economic evaluation were very limited so resort had to be made to a mail survey of key collaborators in the projects, secondary data sources, along with various assumptions and estimates. The sources and bases of these are detailed in the report.