Interferon-tau (IFN-tau) is a secreted conceptus protein which plays a critical role in the establishment of ruminant pregnancy by its antiluteolytic and antiviral effects. In the present study, we hypothesized that IFN-tau expression was temporally and spatially regulated in different pre-implantation embryos and the levels of IFN-tau expression were different among bovine embryos derived from parthenogenetic activation (PA), in vitro fertilization (IVF) and somatic cell nuclear transfer (SCNT). By using in situ hybridization with Digoxingenin (DIG)-labelled IFN-tau cDNA as a probe, we detected IFN-tau mRNA in bovine embryos from days 3 to 9 in culture. However, the timing of the initiation of IFN-tau mRNA expression was different among PA, IVF and SCNT embryos. Interferon-tau mRNA was first expressed in 16-cell stage IVF embryos on day 4, in SCNT morula on day 5 and early PA blastocyst on day 6. Semi-quantitative RT-PCR analysis showed that the expression levels of IFN-tau mRNA did not differ significantly among IVF, SCNT and PA embryos on day 7. In addition, freezing and thawing did not have a major impact either on IFN-tau mRNA expression in IVF or in vivo-produced bovine blastocysts.