Marfan's syndrome (MFS) is a genetic disorder associated with autosomal dominant inheritance. In MFS, the most prevalent cause of death is cardiovascular involvement. Here we introduce a family with a severe penetration of MFS. Eleven members of this family have MFS (father, two daughters, three sons, and five grandchildren). The most common cardiac involvement in our patients was mitral valve prolapse as manifested by mitral regurgitation. At ten years' follow-up, two patients had aortic root dilatation running the risk of aortic dissection; they were, therefore, scheduled for cardiac surgery, during which the Bental procedure was successfully performed. Fortunately, all of the members of this family are currently alive.