Clonidine was clinically evaluated to suppress postoperative shivering in 60 patients who had undergone anesthesia for general, thoracic and vascular surgery. The study was carried out in double blind conditions with comparison of two doses (75 and 150 micrograms) of clonidine, one dose of methylphenidate, and one dose of saline, as control group. The level of inhibition (Goldfarb scale), haemodynamics and temperature were studied. In conclusion, the methylphenidate is drug first choice for postoperative shivering, but clonidine inhibits postoperative shivering without haemodynamic and temperature variations (75 micrograms).