Objective: To determine (1) if braided, polyblend orthopedic suture materials are mechanically superior to monofilament nylon leader and (2) have mechanical properties similar to biomechanical properties of the canine cruciate ligament. Sample Population: Different suture material types. Methods: Mechanical testing was performed on 5 different orthopedic suture materials: 80# test Mason monofilament nylon leader (MNL), FiberTape (FT), FiberWire (FW), Xgen OrthoFiber (XOF), and LigaFiba (LF) using a servohydraulic materials-testing machine. Materials were loaded to failure while collecting data for tensile strength, load at 3 mm and 5 mm of elongation and stiffness. Cyclic elongation of each suture material was tested under physiologic loading between 70 and 150 N for 1000 cycles using 3 mm of elongation to describe excessive elongation. Load at 3 mm of elongation and performance during cyclic testing were compared to previously published physiologic loads in the dog stifle. Results: Ultimate tensile strength was greatest with LF, followed by XOF that was stronger than FT and FW, and the weakest was MNL. LF was the stiffest of all tested materials at 3 mm of elongation. Cyclic elongation was greatest for the MNL elongating 3.75 mm after 1000 cycles. All polyblend braided materials continued to elongate throughout the 1000 cycles under physiologic loads. Conclusions: Polyblend suture materials are stronger and elongate less than MNL in pure tension. The mechanical performance of all sutures tested is questionable when compared with the mechanical demands of the normal stifle in a mid-sized dog.