The aim of the present study is to evaluate the changes in mechanical properties of stainless steel, nickel titanium and beta titanium archwires after clinical use and sterilization. Thirty wires each of Stainless steel, Nitinol and Beta titanium (3M Unitek) were tested in as received (Group A), as received and autoclaved (Group B), and clinically retrieved then autoclaved conditions (Group C). A sterilization protocol of 134 0C for 18 minutes was performed using an autoclave. Mechanical properties were tested using an universal testing machine and the load deflection data was plotted as stress-strain curves from which ultimate tensile strength, elastic modulus as well as 0.2% offset yield strength was calculated. Ultimate tensile strength of Group C archwires showed significantly lower values when compared with Group A and B archwires (P<0.001). Elastic modulus of stainless steel and beta titanium Group C archwires showed significantly lower values when compared with Group A and B archwires (P< 0.001). Elastic modulus of Group Band Group C Nitinol wires showed significantly higher values when compared with Group A archwires (P = 0.03 and P =0.02 respectively). Yield strength of Group C beta titanium archwires showed significantly lower values when compared with Group Aarchwires(P< 0.001). Autoclave sterilization did not affect considerably on mechanical properties of any archwire. Ultimate tensile strength of all archwires were significantly reduced after intraoral exposure.