Researchers have made considerable progress in the development of techniques for the introduction of novel genes into crop plants, but little has been accomplished with soft fruit (Rubus, Ribes, Fragaria and Vaccinium spp.). Cultivars of these crops are highly heterozygous and their genetic structure is maintained by vegetative propagation. A technique which would permit their improvement by the introduction of single genes without disturbing their overall genetic make-up would therefore be extremely valuable. The simplest and most successful method involves the use of the natural gene vector system of Agrobacterium tumefaciens. We describe in vitro plantlet regeneration systems for Rubus, Fragaria and Vaccinium spp. using leaf discs and the use of internodal segments for the regeneration of Rubus (red raspberry, blackberry and Rubus hybrids). We then describe the use of these techniques to regenerate from tissues of red raspberry and blackberry that had been inoculated with A. tumefaciens carrying the marker gene Beta-glucuronidase on the plasmid PBI121.X. A 'CUS' assay was used to confirm that this gene had been successfully transferred from the bacteria into regenerated plants. The techniques developed have provided a method for the introduction of more useful genes into these crops.