One of the desirable attributes of sustainable design in residential construction is to have high thermal mass (HTM) walls. Such wall systems would have large thermal storage capacity and ideally function to absorb direct solar radiation during the day and release the stored heat to the interior during the night. Because conventional residential exterior wall systems generally consist of thin and light screen walls (e.g., exterior light-frame walls with brick veneer or other types of siding), which rely heavily on batt or rigid insulation for thermal purposes, they cannot function as ideal HTM exterior walls. As a result, there is renewed interest in the use masonry walls, which are known to have HTM property. Although the use of masonry as the load-bearing exterior walls is common for low-rise buildings, today's use of load-bearing masonry walls in residential construction may stem from energy efficiency and sustainability considerations rather than the need for a gravity load-bearing system. Nonetheless, the structural behavior of the types of masonry walls that may be considered suitable for sustainable design is a primary concern, given the emerging new masonry materials and in some cases, the use of indigenous materials. In particular, because HTM walls are usually thick and architectural features of sustainable design such as wall setbacks with respect to the roof or re-entrant corners for shading introduce more complicated structural response under lateral loads, additional experimental studies seem to be necessary. In an effort to develop a basic understanding of the structural behavior of HTM walls, a pilot study was undertaken at Penn State University to evaluate the in-plane and out-of-plane capacity of three types of masonry walls some architects use in sustainable designs. The masonry types were chosen to span from the indigenous materials to modern types. For this reason, concrete masonry unit (CMU) was chosen to represent the currently popular masonry type, adobe was chosen to represent the traditionally oldest masonry type used for thousands of years (to be rediscovered today for some sustainable designs), and autoclaved aerated concrete (AAC) was chosen as a relatively modern material. In subsequent sections, a brief background and literature review, the experimental program, and the test results are discussed.