Tumours were incited on leaf sections of Stylosanthes humilis, S. hamata, S. guianensis and S. scalra following infection by Agrobacterium tumefaciens. The suitability of 2 binary vectors (pGA472, BIN6) for gene transfer in S. humilis was tested and kanamycin-resistant tumour tissue was obtained from infected leaf pieces. The presence and expression of the neomycin phosphotransferase (NPT II) gene in the plant cells was demonstrated by hybridization of the coding region of the NPT II gene of the transposon Tn5 to DNA and RNA of kanamycin resistant tumours and by detection of significant NPT II activity in tissue extracts. Tumours also produced teratomatous shoots expressing the NPT II gene, but these could not be rooted.