Genetic sex of most of avian species cannot be identified by the external appearance especially for young birds. Identification of sex in avians can be performed by many techniques, but DNA based methods are more reliable and are most convenient method of sex differentiation in commercially valuable birds or endangered birds. The constitution of sex chromosomes of female birds is ZW and ZZ for males. The DNA sequence that is present only on the W chromosome, which is conserved among species, can be used as a target of PCR-based sex identification. The chromobox-helicase-DNA-binding gene or CHD gene is remarkably conserved in females as CHD-W and has an analogous sequence on Z chromosome (CHD-Z). The specific P₂ -P₈ primers amplify the homologous parts of CHD-W as well as CHD-Z, could be the best way to identify the sex of many avian species. Other molecular methods like RAPD, RFLP, AFLP, micro and minisatellites are some of the efficient sex differentiation techniques in avians.