The ability of nonpathogenic isolates of Fusarium oxysporum (npFo) to induce systemic resistance and defence responses against subsequent challenge with a pathogenic strain of F. oxysporum f. sp. asparagi (Foa) was examined in Asparagus officinalis. In a split-root experiment, roots inoculated with npFo exhibited a hypersensitive response and those subsequently inoculated with Foa displayed resistance. Induction of systemic resistance in npFo-treated plants led to significantly fewer necrotic lesions (P = 0·05) and reduced Foa disease severity compared with plants not treated with npFo. In hyphal-sandwich root inoculation experiments, activities of peroxidase and phenylalanine ammonia-lyase and lignin content were higher in npFo-treated plants and increased more rapidly than in npFo-untreated plants after Foa inoculation. Antifungal activity (inhibition of fungal spore germination and germ-tube growth) from exudates of roots inoculated with Foa were observed for npFo-treated plants but not for npFo-untreated plants. Thus, isolates of npFo may function as inducers of systemic acquired resistance (SAR) and defence responses against Foa invasion in A. officinalis.