This report details the use of cytoplasmic transfer in human oocytes. The introduction of a small amount of ooplasm from a donor oocyte or zygote may alter the function of oocytes, with probable deficiencies. Cytoplasmic transfer from fertile donor oocytes or zygotes into compromised oocytes from patients with recurrent implantation failure after assisted reproduction has now led to the birth of nearly 30 healthy babies worldwide. Transfer of small amounts of cytoplasm probably involves mRNAs, proteins and mitochondria, as well as other factors and organelles. Even though the use of cytoplasmic transfer has been employed in several IVF clinics--and pregnancies have resulted--it is not known definitively whether the physiology of the early embryo is affected. This review outlines the experimental cytoplasmic transfer techniques and postulates the future impact in assisted reproduction.