The ultrastructure of wheat cultivars with slow-rusting resistance expression to the stripe rust, Puccinia striiformis, wasstudied through TEM. The results show that slow-rusting has the same hypersensitive response characters with the lowinfection type resistance, but the mesophyll cell necrotized less in number, thereby only partially inhibiting the extensionof rust fungus, and the fungus being inhibited and necrosed slighter in degree. Apart from the occurrence ofhypersensitiveness, the response of the host cells in slow-rusting wheat cultivars to the infection of fungus also producesstructural materials associated with defense reaction, but distinctly less than that in resistant cultivar. Thus, it is suggestedthat the slow-rusting resistance might have a similar mechanism with the low infection type resistance of race specificity,but with lower intensity. The ultrastructure of wheat cultivars with slow-rusting resistance expression to the stripe rust, Puccinia striiformis, was stutied through TEM. The results show that slow-rusting has the same hypersensitive response characters with the lowinfection type resistance, but the mesophyll cell necrotized less in number , thereby only partially inhibiting the extension of rust fungus, and the fungus being inhibited and necrosed slighter in degree. The response from the occurrence of hypersensitiveness, the response of the host cells in slow-rusting wheat cultivars to the infection of fungus also producesstructural materials associated with defense reaction, but distinctly less than that in resistant cultivar. Thus, it is suggested that the slow-rusting resistance might have a similar mechanism with the low infection type resistance of race specificity, but with lower intensity.