Carbon nanotubes are shown to be modulators of ionic gradients possibly impacting artificial nanophysiology. In contrast with wider nanotubes, the ion traffic inside narrow nanotubes (similar to9.45 Angstrom diameter) eventually reaches steady stoichiometries which may be dramatically different from bulk ratios. The narrow nanotube reduces the polarizability of confined water so that charge imbalances inside cannot be sustained. (C) 2003 American Institute of Physics.