The interaction of crown gall provoking Agrobacterium tumefaciens strains and Ti plasmids isolated from them, with pollen grains from Petunia hybrida as well as other haploid cells from this plant have been investigated. Octopine and nopaline synthesis were used as indication of transformation. Tumours could be induced in all ploidy levels (2n, 3n, 4n) of vegetative P. hybrida tissue including haploid (n), but not in pollen grains.