Ten Fusarium strains were tested for their sensitivity to extracts of Chelidonium majus L. Growth inhibition was measured either in solid or in liquid media. Aqueous extracts had considerable inhibitory action but methanolic extracts showed the best results. Root extracts were more inhibitory than shoot extracts. On the basis of growth inhibition the Fusarium strains were aggregated into five classes, the extremes being Fusarium culmorum plus Fusarium graminearum (quite resistant) and Fusarium oxysporum f. sp. cubense (very sensitive), with the other seven strains occupying the three intermediate classes. The high resistance of most Fusarium strains to conventional fungicides led us to propose C. majus as a good source of substances useful for the treatment of fungal infections, with special importance for those caused by Fusarium.