Borna disease (BD) virus from infected brain tissue of horses or rabbits could be grown in embryonic brain cells from rabbits or rats with high virus yields. The cells became persistently infected and could be subcultivated without loss of infectivity. Cocultivation of infected rabbit brain (ERB) cells with GMK-, Vero-, or MDCK-cells led to persistently infected cell lines. BD virus grown in MDCK cells after cocultivation became adapted to this cell type and could be used directly for further infection of MDCK cells.