A series of dry-stack (mortarless) interlocking block wall systems 3 m x 2.50 m were tested under concentric loading. The blocks comprise earth-cement blocks stacked in stretcher bond without mortar. Further tests were conducted on wall prisms consisting of 4 or 8 blocks. A conventional masonry block wall was also tested for comparison. This paper highlights the experimental set-up and reports the failure loads, typical crack patterns and general structural behaviour of the dry-stack walling systems under in-plane loading. The test results were used as a basis for the development of an empirical model for the prediction of the load capacity of the dry-stack system. (A)