The purpose of this study was to evaluate and compare frictional forces generated between orthodontic brackets and arch wires. Independent variables were chosen for study: arch wire size and shape, arch wire material, bracket width, and second-order angulation between bracket and arch wire. Kinetic frictional forces of stainless steel (0.014″, 0.016″, 0.018″, 0.016″ x 0.022″, 0.018″ x 0.022″), β-titanium (0.016″ x 0.022″) arch wires were measured on wide and junior edgewise twin brackets (0.018″ x 0.022″ slot). Instron was used to pull arch wires while 0°, 3°, 6, or 9° angulation between and wire and bracket was given. The results were as follows: 1. The frictional force of β-titanium wire was larger than that of stainless steel wire. 2. The frictional force was generally increased as the size of wire is increased. 3. The frictional force of rectangular wire was larger than that of round wire. 4. As second order angulation was increased, the frictional force was also increased. 5. The frictional force was larger on a wide bracket than on a junior bracket.