The subject of the article is the theoretical aspects of the effectiveness of the sterilized currency intervention as a means to stabilize the fixed rate. Effectiveness of currency intervention, especially sterilized, is the subject of continuous controversy the resolution of which is searched for in more and more numerous statistical-econometrical empirical studies. In the face of contradictory and ambiguous study results as well as cursory empirical observation a particularly great importance should be attached to theoretical arguments that would provide a ground for interpretation and understanding of empirical observations. The main part of the article constitutes a critical overview of the theoretical views on the ways in which intervention influences the exchange rate. The conducted analysis leads to a conclusion that currency interventions directed to protect the rate level may in some cases be effective, but in others they may be ineffective. Such conclusion is perfectly consistent with the experience gathered. Contrary to the empirical analysis the theoretical perspective allows to look into the intervention mechanism and define the factors that may determine the effectiveness of intervention.