Loop-mediated isothermal amplification (LAMP) is a novel DNA amplification method that amplifies a target sequence specifically under isothermal conditions. The LAMP product is detected by the turbidity of the reaction mixture without electrophoresis. We have developed a rapid sexing method for bovine preimplantation embryos using LAMP. Sexing is performed utilizing two LAMP reactions, male-specific and male-female common reactions, after DNA extraction. The time needed for sexing is <1 h. Sixty-one fresh sexed embryos, of which 23 and 38 had been judged as male and female, respectively, were transferred to recipient animals (one embryo per animal). The pregnancy rate was 57.4% (35/61) and all calves born were of the predicted sex. Therefore, LAMP-based embryo sexing accurately determined gender and was proven to be suitable for field application. In this review, we describe the procedure for detecting male-specific DNA sequence by LAMP for the rapid identification of freemartins. In addition, we also describe an efficient procedure for embryo sexing of water buffalo (Bubalus bubalis) with LAMP. © 2012 Japanese Society of Mammalian Ova Research.