Dissociated canine brain cell cultures were infected with virulent canine distemper virus (CDV). Double immunofluorescent labelling was done to simultaneously demonstrate viral antigen and specific glial cell markers. Virus containing oligodendrocytes were not found at any stage of the infection. A certain proportion of the infected cells were shown to be astrocytes. It was concluded that CDV has no obvious tropism for oligodendrocytes which could explain the mechanism of demyelination in distemper in vivo.