SYNOPSIS Interspecific hybrids are becoming increasingly important to the South African forest industry. Presently, hybrids of the subtropical eucalypts are the most prominent. Many thousands of hectares of selected clonal plantings have been established. The most common hybrid combinations are Eucalyptus grandis crossed with either E. camaldulensis, E. urophylla or E. tereticornis. These hybrids have made it possible to extend tree planting to areas traditionally considered off-site for plantation forestry. On these marginal sites, the hybrids growth and survival outperformed the pure species, and they are consistently more resistant to diseases, pests, cold, heat and drought. Through developing hybrid combinations, land closer to processing sites can now be planted. The wood and growth properties of the hybrids are normally intermediate between the parent species, but superior growth to both parent species is common. Great care must be exercised in selecting the parents for the hybrid combinations, which must be based on performance of both parents from breeding trials. To ensure uniform and consistent end products, wood properties should be considered as it is essential to ensure that the density range of the hybrid is within acceptable limits. The basic wood density of the hybrid is generally higher than that of pure E. grandis, and is influenced by age and site, which in turn will affect the harvesting age. The authors predict an increased operational use of hybrids for the cold-tolerant eucalypts and for Pinus species as vegetative propagation technology improves. Hybrids used commercially must be carefully screened over a range of growing sites to ensure that the selected clones are well adapted for site and product. Mondi is presently screening in excess of 1 000 hybrid clones of which only 1 to 2% will be commercialised.