The wide use of forest-tree products and the progressive deterioration of natural forests mean that foresters can no longer rely on the exploitation of existing forests. Extensive accelerated-breeding programs are needed for reforestation and to improve existing forest-tree species. Plant genetic-transformation techniques and gene isolation and characterization are no longer serious problems; forest-tree species should be a major target for commercial genetic engineering and molecular breeding. We discuss some problems in forest-tree breeding and summarize developments in the transformation of tree species, including possible applications for improving and introducing novel traits into forest tree-species. Copyright (C) 1998 Elsevier Science Ltd.