Ultrastructural alterations in foliar cells were studied in leaves of resistant maize varietyLuyu16 and susceptible maize inbred line Luyuan92 infected by maize dwarf mosaic virus Shandong isolate(MDMV-SD), respectively. The results showed that marked cytopathological alterations were observed both inresistant plants and in susceptible plants, compared with that in healthy plants. However, some ultrastructur-al alterations, which observed in resistant plants, were different from those in susceptible plants. In resistantplants, which infected with the virus, the main organelles, including chloroplasts and mitochondria, wereslightly destroyed, the amount of mitochondria and peroxisome were increased. A few or no plasmodesmatawere observed. There were three kinds of inclusions including pinwheel, bundle and laminated aggregate, andthe virus particles in the cytoplasm. In susceptible plants, which infected with the virus, the chloroplasts wereheavily disrupted, including thylakoid swelling and envelope broking. The virus particles were more than thosein the resistant variety. Four kinds of inclusions including pinwheel, bundle, laminated aggregate and highelecton-dense body appeared in cytoplasm. Plasmodesmata and plasma membrane were abundant, and therewere frequent invaginations of the plasma membrane that led to the formation of vesicles and myelin-likestructures.