Acacias are of considerable social and industrial importance for tropical reforestation, with about 2 million ha worldwide. The last few decades have seen a major expansion of plantations for industrial use, especially in South-East Asia. Both native and exotic species of Acacia are also widely grown in the Indian sub-continent. Turnbull et al. (1998) reviewed the status of tropical acacia plantations in Asia. The species which have been most widely planted so far in industrial plantations in South-East Asia are Acacia mangium Willd. and A. auriculiformis Cunn. ex Benth. A. crassicarpa Cunn. ex Benth. and A. aulacocarpa Cunn. ex Benth. provenance and species trials have been established in many locations throughout the region to provide options for future hardwood plantations. Commercial plantings of A. crassicarpa have recently been established in Indonesia. Plantations of acacias in the humid tropics have been relatively free of disease compared to eucalypts that are commonly damaged by disease in such environments. Reports from several countries in South-East Asia and northern Australia have, however, suggested that the future productivity of acacia plantations may be affected by fungal pathogens. During 1995–96, surveys of diseases of the four Acacia species mentioned above were carried out in northern Australia and several countries of South-East Asia, supported by funding from the Australian Centre for International Agricultural Research (ACIAR) and the Center for International Forestry Research (CIFOR). The surveys by forest pathologists were undertaken in native stands, trials and industrial and social forestry plantations of tropical acacias in Australia, India, Indonesia, Malaysia and Thailand. The objectives were to assess the potential of fungal pathogens as limiting factors to tree growth and productivity, and to compare the relative importance of individual fungal pathogens.