In this paper, the basic concepts concerning the liability of health care institution for nosocomial infections are presented. The principles of ex contracto and ex delicto liabilities, as well as the concept of so-called anonymous guilt are discussed. The range of duties for both the health care institution and the employed medical personnel is indicated, the duties and the consequences of their non-fulfillment are systematized, and the obligatory jurisdiction concerning the functioning of prima facie evidence is considered. The author aimed at explaining the principles governing the civil liability of health care institutions and their employees. Med Pr 2009;60(4):335-343