Tight regulation of pH is critical for the structure and function of cells and organelles. The pH environment changes dramatically along the endocytic pathway, an internalization transport process that is ‘hijacked’ by many intracellularly active bacterial exotoxins, including the anthrax toxin. Here we investigate the role of pH ( 4 - 7.5) on single-channel properties of the anthrax toxin channel, PA63. Even though the PA63 channel ability to bind and translocate the enzymatic components of the toxin has been investigated in a number of studies, pH-dependent behavior of the channel per se has so far remained largely unexplored. Using conductance and current noise analysis, blocker binding, ion selectivity, and PEG partitioning measurements, we show that the channel exists in two different open states (‘maximum’ and ‘main’) at pH ≥ 5.5, while only a maximum conductance state is detected at pH < 5.5. The ‘maximum’ and ‘main’ conductance states are functionally identical and do not reflect dilation of the channel at the ϕ-clamp region. We describe two substantially distinct patterns of PA63 conductance dependence on KCl concentration uncovered at pH 6.5 and 4.5. At pH 4.5, the channel conductance nearly scales with KCl solution conductivity whereas at pH 6.5 the dependence is very weak. Lowering solution pH does not neutralize the channel, which still remains strongly cation selective. We suggest that the PA63 conductance is determined by the two contributing factors: ionic strength-dependent electrical potential and access resistance.