Although rice straw and other grains have been used in building since pre-history, in the past two decades, there has been a move to utilize this rapidly renewable, locally available, agricultural byproduct as part of the sustainable construction movement. Up to this point, this has been done by simply stacking up the full straw bales. Stak Block, invented by Oryzatech, Inc., is a modular, interlocking block made of a composite of rice straw and binding agent that serves as an evolution in straw construction. This study investigates the feasibility of using these Stak Blocks as a structural system. The report was divided into four main parts: material testing, development of effective construction detailing, full-scale physical shear wall testing, and a comparison with wood framed shear walls. The first section investigated the feasibility of using the Stak Blocks in a load-bearing wall application. Constitutive properties of the composite straw material such as yield strength and elastic stiffness were determined and then compared to conventional straw bale. Next, the decision was made to prestress the walls to create a more effective structural system. Various construction detailing iterations were evaluated upon the full-scale shear wall testing using a pseudo-static cyclic loading protocol. Finally, the available ductility of the prestressed Stak Block walls in a lateral force resisting application is quantified along with an approximation of potential design shear forces. It was determined that the Stak Block material performed satisfactorily in gravity and lateral force resisting applications, in some respects better than conventional wood-framed construction, and has great potential as a seismically-resistant building material.