Shells of three different chestnut cultivars named as 'Marigoule', 'Maraval' and '52112' ('Vakit Kestanesi') were tested for their antifungal activities against Penicillium roqueforti, Aspergillus niger and Aspergillus parasiticus. Ethanol extracts were obtained by soxhlet extraction and antifungal activities were determined with three point inoculation method and an automated quantitative assay by absorbance measurement at 595 nm on a microplate reader. Results of the two methods demonstrated that ethanol extracts of 'Marigoule' and 'Maraval' retarded the growth of Aspergillus niger but did not inhibit it completely. None of the three extracts inhibited Penicillium roqueforti according to microplate assay; but on the contrary stimulatory effects of '52112' on the mentioned mould were determined. Contradictory results were obtained from two methods concerning the antifungal effect of three extracts, so further studies are needed for the factors causing variations between two methods and the composition of the chestnut shell extracts to determine the antifungal activity more accurately.