The interaction between Puccinia recondita f. sp. tritici (now widely referred to as P. triticina) and endophytic fungi in wheat was examined in laboratory experiments to determine whether the presence of fungal endophytes suppresses leaf rust disease caused by this fungus. Endophytes and cell-free washings from culture plates of the endophytes reduced the density and size of pustules in a susceptible cultivar when inoculated 3, 7 and 14 d prior to the pathogen. Disease at 12 d was reduced when the endophytes were inoculated simultaneously up to 50 mm from the fungus. Interactions between endophytes and this Puccinia are most probably mediated by defence mechanisms induced in the host plant.