BACKGROUND: Rates of type B dissection are nearly double those of type A in Marfan syndrome. However, data surrounding clinical and surgical outcomes of type B dissection and associated life expectancy are limited. METHODS: We investigated outcomes and survival of type B dissection in a large, single-center Marfan syndrome registry. RESULTS: Fifty of 362 (13.8%) patients experienced a type B dissection, with a median postdissection follow-up of 8.9 (interquartile range, 3.9-15.4; range, 0-33.4) years. Although dissection rates were comparable in men and women (14.4% versus 13.4%, P=0.78), dissection occurred at an earlier age in men (36 versus 46 years, P=0.025). Seventeen (34.0%) patients required early (<3 months) open thoracoabdominal repair, 17 (34.0%) had late surgery, 14 (28.0%) were managed medically, and 2 (4.0%) suffered rupture with death. Life expectancy was shorter in those with versus without type B dissection (median survival, 71.1 versus 78.5 years, respectively; P=0.02), but only in men due to earlier age at type B dissection (median age, 60.4 versus 71.1 years; P=0.004) with comparable postdissection life expectancy. Postdissection survival did not differ on the basis of timing of surgery or medical management. Eleven patients (5.9% of those with prior root replacement) suffered a distal anastomosis dissection at a median of 18.0 (interquartile range, 12.1-23.1) years postoperatively, of whom 9 required surgery after a median of 0.59 months (interquartile range, 0.13-12.3). CONCLUSIONS: Type B dissection in Marfan syndrome is associated with a shortened life expectancy, but only in men, and usually requires surgical intervention. Distal anastomosis dissection is an underappreciated, important complication after proximal aortic surgery.