Cytopathic effects in orchid leaf tissues infected with Australian, Japanese and Brazilian isolates of Orchid fleck virus (OFV) were indistinguishable and like those previously described in the literature. Cells had an electron-lucent viroplasm with unenveloped rod-shaped virions in the nucleus and cytoplasm, often associated with the inner membrane of the nuclear envelope and the endoplasmic reticulum. Antiserum raised against a Japanese isolate of OFV reacted with Brazilian and Australian isolates in ELISA, and when used for immuno-gold labelling, also reacted in situ with the rod-shaped virions and the intranuclear viroplasm of all three isolates. These results suggest that the viroplasm is where structural proteins accumulate and virions are formed.