An accurate, sensitive, and quick method for determining the sex of ovine embryos was developed using polymerase chain reaction (PCR) primers derived from an ovine-specific Y-chromosome (SRY gene; GenBank Acc. Z30265), amplifying a 166 bp DNA fragment in male samples. To increase the sensibility and specificity of the technique a duplex PCR was carried out, using one pair of ovine-specific primers (CGN gene: GenBank Acc. AY785290) and one pair of Y-chromosome-specific primers. CGN fragment provides an internal positive control for amplification. Using this method we can determine the sex up to 20 pg of DNA from blood. In the same way, sex of embryos was determined from two cells.