The patch clamp measurements carried out on the patch of the cell membrane showed that amphotericin B (AmB) applied at a low concentration (0.05 and 0.1 µM) causes a decrease in seal resistance, indicating loss of membrane tightness. Application of AmB also decreased the number of active outward rectifying potassium channels TOK1, but did not change the unitary conductance of the channels. Interestingly, AmB did not significantly change the open probability of the single channel. Such results indicate a lack of direct interaction of AmB and the channels. Membrane permeability changes after AmB were also observed by fluorescent microscopy. This research allowed us to conclude that integrity of the membrane between the pores formed by AmB is maintained. Supported by NCN grant DEC-2012/05/BNZ1/00037