Obtaining resistance against fungal diseases in plants is still a great challenge for the breeders. An alternative strategy is to introduce genes encoding antifungal enzymes into the host plant genome. Trichoderma species are known to have strong antifungal effect partly as a result of their production of extracellular chitinase enzymes, which hydrolyse the main constituent of the fungal cell wall. The 42 kDa endochitinase gene of Trichoderma hamatum was introduced to Nicotiana tabacum plants under the control of the Ca35S promoter and the NOS terminator. The transformed plantlets grown on selective medium showed no morphological or physiological difference as compared to the wild type plants. They all were positive in PCR tests performed to screen a 164 bp sequence of the Trichoderma endochitinase gene. The sequence of the amplified fragment was analysed and showed 100% homology with the Trichoderma hamatum endochitinase gene. We did not detect homology with plant origin chitinase enzymes. Compared to the untransformed control, all transgenic lines showed higher tolerance for Botrytis cinerea in fungal infection experiments. The endochitinase gene could be detected in the first and the second progeny of the transformed lines, too.