This study was undertaken to investigate the mechanical behavior of bonding wires. Beryllium doped gold and aluminum 1-percent silicon wires from three different manufacturers were tested to determine the elastic, tensile and load relaxation properties. The stiffness (modulus) of the wires was found to depend on the method of fabrication as well as on thermal and mechanical history. Although the specified breaking load and elongation values of the wires were essentially the same, load relaxation tests revealed substantial differences in the time dependent flow properties of the wires. Low temperature annealing, which was performed to simulate prolonged storage of the wires, resulted in changes in the properties of both the gold and the aluminum 1-percent silicon wires.