Attempts to obtain fertilization of sheep ova recovered from follicles and deposited in the oviducts of the same ewes were unsuccessful. The recovery and transfer of postovulatory one-cell ova was successful if the paired ewes were closely synchronized as to the end of oestrus. Fertilization apparently was completed soon after the end of oestrus in mated ewes and ova from non-mated ewes were apparently still capable of normal fertilization and development at this time. Ova from non-mated ewes usually do not have corona cells present when recovered from the oviduct. Both fertilized and unfertilized ova appear to be able to withstand stress associated with a single transfer, but a second transfer greatly reduces the chances of a successful pregnancy.