Aluminium-fly ash powder mixtures containing 5-20 wt % fly ash were prepared using both precipitator (solid) and cenosphere (hollow) fly ash particles. These were compacted at pressures ranging from 138-414 MPa. Spring back, densification parameter, green density, green hardness and green strength of the compacts were determined as a function of compacting pressure and weight per cent of fly ash. It was observed that the spring back, green density and green strength of the compacts increased with increasing compacting pressure. Green density, green strength and green hardness of the compacts decreased, and the spring back increased, with increasing weight per cent of fly ash particles, the cenosphere particles leading to a higher spring back as compared to solid precipitator particles. At compacting pressures of the order of 345 MPa, the solid fly ash particles generally remained intact, and well distributed in the matrix, but the hollow cenosphere particles collapsed, and outer shells were present in the matrix in layered forms.