This study introduces the development of a new, experimental setup using all enhanced triaxial tester and a new methodology for the characterization of fine particulate systems in all aerated condition. Tests were performed using the new setup to study the effects of aeration on two different powders: a highly cohesive precompacted powder and a cohesionless powder, the former being microcrystalline cellulose PH-102, mean particle size 90 mum, and the latter alumina powder, mean particle size 100 mum. The degree of aeration was small and it was of the same order of magnitude as the velocities encountered during the entrapment of air in filling and during other handling processes. The superficial velocity for aeration was about three orders of magnitude lower than that required for fluidization. The immediate results have shown that even a small amount of interstitial air has a dramatic effect on the quasi-static strength and an obvious effect on the elastic parameters of the powder. The quasi-static strength of the alumina powder was reduced by about 20%, at a superficial air velocity qf 0.02 m/s, whereas the quasi-static strength of microcrystalline cellulose was reduced by about 17%, at a superficial air velocity of 0.009 m/s. The Young modulus values were reduced by about 13% on average and the bulk modulus values by about 8% on average for microcrystalline cellulose for the air velocity given above.