Recently, cloned mice have been produced using cells derived from a drop of peripheral blood [8]. Kamimura et al. [8] used putative granul es and/or monocytes and lymp arately, and obtained 2.1% and 1.7% birth rates, re (P> 0.05). B and T lym- phocytes ate a portion of thei geno during dif- orme erentiation. The very low cloning ciency in terms of blastocyst develop (0%-3%) and failure in