The ultrastructural changes in leaf cells of Chenopodium quinoa caused by Arabis mosaic virus (ArMV) infection have been investigated in electronmicroscopic studies. The techniques of negative staining and embedding sections from leaves in epoxy resin were applied. ArMV virions have been found in the cytoplasm and either singularly scattered or forming different arrangements in the vacuoles as well. Tubules with virions have been observed only rarely. Two types of inclusions have been identified and their structure illustrated. Ultrastructural changes in leaf cells of C. quinoa caused by ArMV infection are partially similar and partially different from those occurring on Phaseolus vulgaris plants infected with ArMV. It might suggest that some ultrastructural changes are typical for the virus and some are characteristic for the host plant.