The production of cloned animals is a difficult and complex procedure that requires two basic steps. First, the cytoplast must be prepared by the enucleation of metaphase II oocytes. Second, the nucleus is transferred either by fusion or direct microinjection into these cytoplasts. The classical mechanical enucleation of metaphase II oocytes is rather difficult, requiring good equipment and considerable micromanipulation skill. For this reason the simplification of this step is permanently in the centreof interest of those scientists who are involved in the production of clones.