Abstract. Conidia of the phytopathogenic fungus Calonectria morganii were transformed to hygromycin B resistance using the hph gene of Escherichia coli as the selective trait, governed by a heterologous fungal promoter and the Aspergillus nidulans trpC terminator. Agrobacterium tumefaciens-mediated transformation yielded stable hygromycin B-resistant clones (average number106 per 107conidia). Putative transformants appeared to be mitotically and meiotically stable. The presence of the hph gene was checked by PCR. In four randomly chosen transformants, single-copy integrations of the marker gene at different chromosomal sites were proven by Southern analysis.