Many aspects of the association of Polymyxa betae with beet necrotic yellow vein virus during transmission have not been elucidated. In order to study the specificity of virus acquisition by the vector and its transmission to the host, thin sections were made through sugar beet roots infected both by the virus and the fungus. Immunogold labelled virus was identified at different stages of the fungus (plasmodia, zoosporangia and mature zoospores). However, specifically labelled clusters of virions have not yet been observed in mature resting spores.