Pregnancy in a rudimentary horn is a rarely encountered form of ectopic pregnancy and is often an emergent situation because of the risk of rupture of the horn. A 31-year-old gravida 3 para 1 woman with 7 to 8 weeks' gestational age was found to have a viable pregnancy in a rudimentary noncommunicating horn of a unicornuate uterus. She elected termination of the pregnancy via local intracardiac lidocaine and intra-amniotic methotrexate injections. Subsequent removal of the rudimentary horn was necessary to prevent recurrence. Because of the risk of rupture, the diagnosis and management of an ectopic pregnancy in a rudimentary horn can be emergent.