This unit describes the propagation of Borrelia burgdorferi as well as other "cultivable" Borrelia species in Barbour-Stoenner-Kelly-II (BSK-II) medium. It supplies a detailed recipe for BSK-II, as well as protocols for standard liquid culture, the generation of frozen Borrelia stocks, and the plating of B. burgdorferi cells in solid BSK-II medium.