Cultured stem fragments from the monocotyledonous plant Asparagus officinalis infected by the oncogenic bacterium Agrobacterium tumefaciens developed tumorous proliferations. This tissue was propagated in vitro on hormone-free culture medium. The T-DNA-encoded markers nopaline and agrocinopine were unambiguously detected in these tissues. The data demonstrate that stable T-DNA transfer as well as expression of T-DNA genes is possible in at least some monocotyledonous plants. This opens new possibilities for plant genetic engineering using the Ti plasmid as a gene vector.