There have been many recent reports of the successful production of large numbers of in vitro matured (IVM) and in vitro fertilised (IVF) cow ova. While a high proportion (80-90%) of oocytes undergo apparently normal maturation and fertilisation in vitro, only 15-20% develop in vitro to the morulae and blastocyst stages. Early cleavage stage in vivo matured and fertilised cow ova also encounter a developmental “block” at the 8-16-cell stage during in vitro culture in conventional culture media. However, this block has been readily overcome by co-culture involving the use of bovine oviducal cells, with up to 80% of 1-4-cell ova developing to morulae and blastocysts: The present study examined the development of IVM-IVF cattle ova removed at 24 or 48 hours from the insemination medium and cultured on cattle oviducal cells and also compared the development of IVM-IVF and in vivo produced ova in the same oviducal cell co-culture system.