The mechanical properties of canine anterior cruciate ligaments are studied at different strain rates in different environments. A tibia-anterior cruciate ligament-femur preparation is tested preventing rupture at points of attachment. The data is compared with other investigations of ligaments and tendons and is plotted by use of the constitutive equation proposed by Y. C. Fung. Good agreement is obtained using Fung's exponential relationship and two numerical parameters are suggested for evaluation of future test data.