background: overweight and obesity affects approximately 1.7 billion people, with increase in morbid obesity of 80% for women and 400% for men, since 1970. metabolic syndrome is a complex disorder associated with insulin resistance and abdominal obesity, causing changes in glucose metabolism in various tissues and hyperinsulinemia. aim: to verify changes in the pre and post-operative parameters in morbidly obese patients with metabolic syndrome who underwent to roux-en-y gastrointestinal bypass. method: seventy four patients with obesity with metabolic syndrome submitted to gastrointestinal bypass roux-en-y were included. all of them had measured waist-hip ratio, blood pressure, total cholesterol, hdl, ldl, triglycerides and fasting glucose pre-operatively and at the first and fourth month post-operatively. results: in the first post-operative month, happened a weight reduction of 7.96%, bmi of 8%, waist-hip ratio of 1.35%, total cholesterol of 17.95%, hdl of 14.5%, ldl of 15.31%, tag's of 30.29% and 9.75% of glucose; on the fourth month was observed a weight reduction of 14.94%, bmi of 20.08%, waist-hip ratio of 5.96%, total cholesterol of 21.27%, hdl of 3.53%, ldl of 23.72%, tag's of 29.6% and 10.34% of glucose. conclusion: all the parameters evaluated in this study had a statistic significant improvement, with the exception of hdl-cholesterol.