Objective: to compare the frictional forces generat Objective: ed by two types of active self-ligating brackets and conventional bracket. Material and methods: Material and methods: ial and methods: Two types of active self-ligating brackets (In-Ovation R, GAC International, Bohemia, NY), (SPEED, Strite Industries, Cambridge, Ontario, Canada) and one conventional bracket (Synergy, Rocky Mountain Orthodontics, Denver, Colo). Each bracket was tested with 0.016X0.016", 0.016X0.022" and 0.017X0.017" (Rocky Mountain Orthodontics, Denver, Colo) stainless steel wires. low-friction opaque ligatures (Rocky Mountain Orthodontics, Denver, Colo) were used for synergy brackets .The universal testing machine was used to measure the frictional resistance for each bracket/wire assembly. Results: Results: Results: SPEED brackets produced a significantly (P< 0.001) more frictional resistance than both In-Ovation R and Synergy brackets with all archwires' sizes. While, there was no significant difference between frictional forces of Synergy and In-Ovation R brackets (P>0.05). frictional forces increased significantly in all bracket-archwire combinations (P< 0.001) as wire size increased from 0.016X0.016"to 0.016X0.022" and 0.017X0.017" respectively. Conclusions: Conclusions: Conclusions: SPEED SL brackets produced more frictional forces compared with Synergy and In-Ovation R brackets. The frictional resistance increased as wire size increased From 0.016X 0.016" to 0.016X0.022" and 0.017X0.017". Synergy brackets combined with the low- friction ligatures is considered a proper choice for sliding mechanics.