An acardius is a monster that sometimes develops in single-ovum twin pregnancies as the resutls ofinequalities in the communicating placental circulation. One twin is well developed and normal, whereas the otheris imperfectly formed, with either a rudimentary-hemiacardius or an absent heart-holoacardius. The most commonvariety of the holoacardiac monster is the acephalus, or headless fetus. Authors report a case of acardiumacephalus twins associated with hydramnios in a 28 years old, para 1-0-0-1, diagnosed amorphous twins with serialsonograms, terminated in the 23th week prequency and the other in 1 25 years old, para 0-0-0-0, diagnosed twinswith FDIU in sonogram. We present these two cases with brief review of literatures.