Inherited connective tissue disorders, among them Ehlers-Danlos syndrome, osteogenesis imperfecta, Marfan syndrome, and Larsen syndrome, are characterized by generalized joint hypermobility. Others, such as Morquio syndrome or achondroplasia, have hypermobility in a more limited distribution. Recent clinical and molecular genetic studies have defined the range of clinical variation and the underlying molecular defects in several disorders. These studies provide hope that more common varieties of joint hypermobility can be understood and that effective therapies are within reach.