A rare case of rupture of a noncommunicating rudimentary horn pregnancy is presented. The pregnancy continued to 16-weeks' gestation, when the rudimentary horn ruptured. The patient had signs and symptoms of massive hemoperitoneum. An emergency exploratory laparotomy revealed a ruptured rudimentary horn and an intact amnionic sac. Prompt excision of the rudimentary horn was performed. The relative literature and factors associated with a rudimentary horn pregnancy are reviewed and discussed.