Twin births in some Iranian sheep breeds arecommon, though infertility is scarcely detected.Our investigation on GDF9 mRNA extracted fromabattoir-derived ovaries showed that there were 3point mutations including two conservative substitutions,G2 (C471T) and G3 (G477A), and onenon-conservative mutation, G4 which replacesglutamic acid to lysine (E241K) in the unprocessedprotein. The gene discussed is GDF9; the disease is Infertility.