The Chinese white poplar (Populus tomentosa Carr.) is susceptible to infection by plant diseases which severely affect its growth and substantially decrease its economic value. A chitinase gene (Bbchit1) from Beauveria bassiana was introduced into Chinese white poplar (Populus tomentosa Carr.) by Agrobacterium-mediated transformation. The T-DNA of plant transformation vector contained the beta-glucuronidase reporter gene (GUS) under the control of CaMV 35S promoter and the neomycin phosphotransferase selection marker gene (NPTII) driven by the nos promoter. GUS activity was detected in most of the kanamycin-resistant plants tested. Stable integration of transgenes in the plant genome was confirmed using PCR. RT-PCR analysis showed that the Bbchit1 gene was transcribed in the transformed plants. When evaluated for resistance to poplar fungal pathogens with an in vitro assay, crude extracts from leaves and shoots of transgenic lines were inhibitory against the pathogenic fungus Cytospora chrysosperma (Pers.) Fr. Similarly, Bbchit1 overexpression enhanced disease resistance to C. chrysosperma in the transformed poplar plants, indicating that is gene is potentially useful to protect the trees against fungal diseases.