Abstract: The infusion system is provided with a control device (10) wherein a plurality of influence factors with different physiological action mechanisms, i.e. a plurality of semantic domains, is considered as fuzzy information in the automatic dosing of drugs and the semantic significance of the individual domains is taken into account. The control device (10) for controlling at least one infusion apparatus (21) comprises a plurality of fuzzy control units (17,19) structured in a hierarchical system. On a first hierarchical levels, all linguistic variables, measurement values and derived values are examined by a semantic analyzer (16) with regard to the significance of their contents for the various semantic domains. In a unit (18) for evaluation of semantic domains, the results of the above examination are passed through a plurality of evaluation stages to draw conclusions on the operation on a second hierarchical level on which each semantic domain is represented by a fuzzy control unit (19) of its own.