Thiazolidinediones have been shown to reduce the development of diabetes mellitus in animal models of type 1 diabetes and to reduce the death of beta cells (cells that make insulin) in petri dishes. Pioglitazone is a thiazolidinedione currently approved for the treatment of type 2 diabetes. This study explores the question of whether pioglitazone can preserve beta cell function in patients with recently diagnosed type 1 diabetes mellitus.