The catastrophic effects of recent earthquakes have drawn the attention of the civil engineering community to the priority of developing effective means for increasing the seismic resistance of structures. Verification of the performance of new seismic resistant systems requires extensive testing under realistic conditions. Seismic simulators are one of the principal tools used for this type of testing. This paper presents the design and development of a 1.1 m. x 1.5 m unidirectional earthquake simulator for testing small-scale structural models in the Universidad del Valle Earthquake Engineering and Structural Dynamics Laboratory.