Triaxial compressive tests have been conducted on CYMAT closed-cell aluminium foams of five different relative densities to investigate their initial failure surfaces under multiaxial loading. Quasi-static uniaxial compressive and tensile tests have also been performed to obtain their uniaxial strength. The experimentally measured yield surfaces are compared with various published phenomenological yield surface models. Reasonable agreement has been observed when suitable Poisson's ratios are employed. Triaxial compressive tests have been carried out on foams with nominal relative density of 17% at various axial loading velocities to study the effect of strain rate on the initial failure surface. The results showed that the initial yield stresses of CYMAT closed-cell aluminium foams are not sensitive to the axial strain rate ranged from 10-4 to 10+1 s-1.