The in vitro susceptibility of Helicobacter pylori to extracts of Eucalyptus camaldulensis Dehnh. and Eucalyptus torelliana F. Muell. (Myrtaceae), Nigerian medicinal plants, was investigated in six strains of H. pylori, namely, ATCC 4504, ATCC 47619, A2, TI8984, 019A, and A6. The susceptibility of these strains was determined using a standardized agar dilution method (National Committee for Clinical Laboratory Standards guidelines) with Mueller-Hinton agar, supplemented with defibrinated horse blood. The minimum inhibitory concentrations of the crude extracts against all the tested strains ranged from 12.5 to 400 mug/mL. Phytochemical screening of the plant extracts revealed the presence of tannins, saponins, and cardenolides. The anti-H. pylori activities demonstrated by these plants may be attributed to their chemical constituents, and explain their reported traditional uses, as well as their gastroprotective properties as demonstrated previously in experimental animals. The results of this work suggest that, in accordance with their traditional medical use in Nigeria, E. camaldalensis and E. torelliana have some therapeutic potential against H. pylori, and thus are of interest for the treatment of H. pylori infections.