Tropical acacias are of considerable social and industrial importance for tropical reforestation and it is expected that about 2 million hectares will be established in Southeast Asia by the year 2000. Recent reports from Malaysia, Indonesia, Thailand and northern Australia suggest that the future productivity of some important species may be constrained by fungal pathogens including leaf spots, shoot blights, stem cankers, heart rot and gall rusts. This study is undertaking a series of case studies of diseases of tropical acacias in native stands, trials and operational plantings in India, Malaysia, Thailand, Indonesia and Australia. Scientists are assessing the extent to which fungal pathogens limit tree growth and productivity and also the relative importance of individual fungal species.