Abstract
The chapter explores the position of both relevant Czech leftist parties, ČSSD and KSČM, in the party system and analyzes the dynamics of their relations (in three phases: from benevolent noncooperation, via hostile noncooperation, up to "cold"/conditioned cooperation). The main emphasis is put on systematic pressure to the organizational change of ČSSD and on anticommunism (as well as its time contingent variant antiparoubkism) as a crucial factor shaping the playground on which Czech left operates, an instrument aimed primarily - in spite of its name - against the Social Democracy