Acardia is a very rare congenital anomaly occurring in less than 1 in 35,000 deliveries. Acardiac parabiotic twin has been reported only in multiple, monochronic pregnancies. This anomalous fetus is sustained in utero by parasitic anastomoses to the circulation of its usually normal co-twin and is therefore not compatible with extrauterine survival. A case of an acardiac parabiotic twin is described, and the literature concerning the incidence, classification and etiology of acardiac is reviewed.