The birth of the clone animals is influencing the frontier of research of animal biotechnology. It has effects on research of animal biotechnology itself by necessitating setting of new research subjects, modifications of the strategy of ongoing research projects, and challenges to schemes formerly considered impossible. In my talk, such topics including mass production of fertile ova and oocyte maturation will be discussed. (1) Oocytes are needed for the production of a clone by nuclear transplantation. Mitochondrial DNA inherited via the oocyte are involved also in the morphogenesis. Therefore, oocytes from the same animal must be used as recipients to produce genuine clones by nuclear transplantation. Experimenting on the assumption that selective oogenesis can be avoided, and apoptosis of oocytes can be prevented, by using ovarian angiogenic factos will be introduced. (2) It is important to clarify the factors of oocytes involving in reprogramming of somatic cells. Such factors are thought to be expressed in oocytes during oogenesis and oocyte maturation. Therefore, molecular mechanisms of oogenesis and oocyte maturation must be clarified extensively. Topics in this field including our recent advances will be discussed. (중략)