In single infection of Tobacco mosaic virus-U1 (TMVU1) or Pepper mild mottle virus (PMMoV), mosaic symptoms were produced on the chili pepper cultivars of ``Cheongyang`` and ``Wangshilgun``. However, in cultivars of ``Manitta`` and ``Bugang``, no symptoms were occurred. In single infection of Pepper mottle virus (PepMoV), symptoms of mottle and malformation were produced on the tested cultivars of ``Manitta``, ``Bugang``,Cheongyang``, and ``Wangshilgun``. In the cultivars of Cheongyang`` and ``Wangshilgun``, synergistic symptoms of stunt and lethal death were induced by mixed infections in the two combinations of TMV-U1+ PepMoV and PMMoV+PepMoV. However, in cultivars of Manitta`` and ``Bugang``, synergistic symptoms were not noted, but mottling which was milder than that of single infection was produced. Cells infected singly with TMV-U1 and PMMoV in the cultivars of ``Cheongyang`` and ``Wangshilgun``, respectively, had the typical ultrastructures of tobamovirus as the stacked-band structure and multiple spiral aggregate (SA). In the cells and tissues infected with PepMoV on the cultivars of ``Cheongyang``, ``Wangshilgun``, ``Manitta`` and ``Bugang``,the potyvirus inclusions of pinwheels, scrolls, lamminated aggregates and amorphous inclusion were observed.In the cells infected mixedly with combinations of TMVU1+PepMoV and PMMoV+PepMoV, the virus particles and inclusions of the two different viruses were found simultaneously in the same cytoplasm. The amounts of virus particles in mixed infections were more abundant than in single infection. The angled-layer aggregates (ALA) were observed only in the cells infected with both TMV-U1 and PepMoV.