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.