Harmonic scalpel is a new surgical instrument. Its use has been recommended in patients submitted to total thyroidectomy. Few randomized controlled trials has been published. However they had small sample sizes, used intermediate outcomes and included different surgical procedures. Our objective is to asses the use of Harmonic scalpel in patients submitted to total thyroidectomy using surgical complications, operative time, drainage volume, postoperative pain, length of stay and costs as outcomes. Our hypothesis is that Harmonic scalpel decreases operative time,drainage volume, postoperative pain, length of stay and costs without increasing surgical complications