The filamentous particles of poplar mosaic virus (PopMV) were detected in palisade, mesophyll and parenchyma cells of systemically infected leaves of Nicotiana clevelandii and N. megalosiphon. The particles were sometimes found scattered throughout the cytoplasm, but more often they occurred loosely associated within ovoid aggregates (up to 3.5 × 1.5 µm) adjacent to chloroplasts and/or mitochondria. PopMV did not induce the formation of ‘pinwheeF inclusions, nor other conspicuous ultrastructural or cytopathic effects in infected cells. These observations provide additional evidence that PopMV is a Carlavirus and not a Potyvirus nor a mite-borne virus. PopMV particles were also detected occasionally within plasmodesmata.