Recent investigations of musculoskeletal disorders, diseases, and treatments have focused on small animal models and specimens of human tissue. These studies require mechanical testing equipment that operates under low force conditions. This proposal requests a low-force, high-performance mechanical testing system to meet the needs of investigators studying the skeleton in mouse and rat models and those examining mechanical properties of human skeletal tissues. Current systems available at our institution are unsuitable because they were originally designed to test large specimens such as whole human bones. The force range, actuator displacement, dynamic performance and axial capabilities are all inappropriate for the high precision and accuracy required for characterizing small skeletal specimens. The requested equipment is versatile, reliable, adjustable for multi-axial loading, and is able to resolve very low forces and torques and extremely small displacements and angles of twist. Fixtures and accessories are requested for testing both soft and hard biologic tissues of very small sizes and to maintain controlled environments. The equipment will be shared among many users connected by basic studies of the skeleton. Major users are studying diverse areas including models of disease and treatment, basic studies of chemical composition and mechanical function, and gene mutation models and the resultant bone phenotype. The high performance mechanical testing system will be incorporated into the existing Core Center for Skeletal Integrity.