The screen-printing (thick-film) technology is widely used for the mass-production of disposable electrochemical sensors. The practical utility of screen-printed electrodes has been developed despite the fact that little is known about the nature of electrode reactions at these important microfabricated sensors. Given the complexity of carbon electrodes, in general, and differences in the composition of commercial carbon inks (used for fabricating screen-printed sensors), the question arises how such differences and complexity affect the electrochemical reactivity. The aim of the present work was to compare the electrochemical behavior and electroanalytical performance of thick-film carbon sensors fabricated with four different commercial carbon inks. The resulting sensors exhibit a wide range of electrochemical reactivities for benchmark redox systems and different background currents. Such differences have a profound effect upon the electroanalytical performance, as was indicated from pulse-voltammetric, amperometric and stripping operations. The choice of the carbon strip (ink) should depend upon the specific technique used.