Nano-scale aluminum particles are innovative materials which are used increasingly in energetic formulations. In this contribution, the theological behavior of suspensions with either paraffin oil or HTPB as the matrix fluid and nano-scale aluminum (ALEX) as the dispersed phase is described and discussed. The paraffin oil/aluminum suspensions exhibit non-Nemonian flow behavior over a wide range of concentrations, whereas the HTPB/aluminium suspensions exhibit 'Newtonian behavior (i.e. the viscosity is independent of shear stress) up to a concentration of 50 vol.% aluminum. Both systems have unusual viscoelastic properties in that their elastic moduli are independent of the solids concentration.