This thesis presents the results from in-plane cyclic testing of a reinforced cob wall. Cob is an earthen building material composed of sand, clay, straw and water. Cob is typically constructed with no steel reinforcement; however, the California Building Code requires reinforcement in all buildings for resisting seismic forces. The purpose of this thesis is to provide additional technical data to integrate cob into the building code. Test results are reported for a 7’ x 8’ x 14” wall with two layers of welded wire steel reinforcement constructed on a reinforced concrete foundation. In-plane cyclic loading was performed on the wall up to a maximum displacement of 3.5 in. Compression tests of sixteen 3.5” x 3.5” cubes were conducted to determine the compressive strength and the modulus of elasticity of cob. Results provide observed performance, displacement components, yielding points and seismic response modification factors. A numerical model was developed to conduct a parametric study considering the variation of several material and structural properties. In addition, discussion of material properties and recommendations for future work are included.