The ligamentous contribution to elbow joint stability is a product of morphology and biologic parameters of each of the collateral ligaments. Better understanding of these characteristics is of paramount importance for successful ligament reconstruction in the surgery for joint replacement and traumatic injury. Two experiments were performed. In the first, the arc of elbow flexion where the individual ligament was either taut or slack was measured; in the second, the structural properties of each collateral ligament were determined by using bone-ligament-bone preparations. The anterior medial collateral ligament (AMCL) and radial collateral ligament (RCL) were taut throughout most of the entire arc of flexion. The posterior medial collateral ligament (PMCL) was taut only when the elbow was in a flexed position. Among the collateral ligaments, the AMCL was the strongest and stiffest with an average failure load of 260 N. The palmaris longus tendon, the most frequently used graft for elbow ligament reconstruction, was similar in strength (357 N).