Two classes of ionic inorganic nanotube (IINT) are predicted to form within carbon nanotubes via the use of ion-based computer simulation models. These structures can be rationalised (and labelled) in terms of folding infinite two-dimensional sheets of hexagons and squares, respectively. Many of the formed IINTs appear 'twisted' (and hence are stereochemically active) and is shown to be a result of the strong electrostatic interactions which control these structures. Such filling offers the opportunity of producing IINTs in a highly controlled (morphological and stereochemical) fashion. Furthermore, the electronic properties of these tubes should be tunable. (C) 2004 Elsevier B.V. All rights reserved.