The influence of the pre-ovulatory oestradiol-17ß (E₂) surge on yield of viable embryos was studied in 28 oestrus synchronized SAMM ewes. Ewes were super ovulated either with FSHo (88 units in 6 divided doses) or PMSG (1200 IU). Blood samples for E₂ were drawn at 4-h intervals for 48 h after progestagen sponge withdrawal. Each ewe was mated six times by natural service. Embryos were recovered on the sixth day after oestrus. Ewes, which received FSHo had significantly higher (p < 0.05) ovulation rates and total ovarian responses (p < 0.01) than those treated with PMSG. Higher recovery rates (p < 0.01), fertilization rates (p < 0.01), percentage (p < 0.01) and yield (p < 0.05) of viable embryos were also obtained for FSHo than for PMSG treatment. Although the timing of the E₂ surge in relation to sponge withdrawal varies with the super ovulatory treatment, no relationship between peculiarities of the surge and embryo characteristics could be established.