© Edinburgh University Press.When autoclaved lightweight concrete (ALC) blocks are bonded with thin-bed mortar to build ALC structures, the structural performance of ALC prisms is as important as the material performance of the ALC blocks. In this study, the compressive performance of ALC prisms was experimentally evaluated. The main test parameters included compressive strength of ALC blocks and use of glass fiber reinforced polymer (GFRP). The test results showed that the compressive strength of the ALC prisms was 59~80 % of that of the ALC blocks, even though relatively high strength mortar was used. The effect of thin-bed mortar on the compressive strength was not significant. The compressive strength of ALC prisms specified in Eurocode 6 overestimated that of specimens with dry density of 350 kg/㎥ and underestimated specimens with dry density of 500 kg/m3. The effects of GFRP reinforcement on the compressive strength and deformation capacity after peak load were negligible. The modulus of elasticity of the ALC prisms increased in proportion to the compressive strength of the ALC blocks. The Poissons ratio was measured at 0.17~0.43, which indicates that the shear modulus can be estimated on 0.4 as specified in current design codes.