Material and Methods: Eggs were divided into five groups of 60, one control group receiving distilled water and four test groups. All groups were placed inside the incubator. Injection of anti-aromatases was performed in fifth day of incubation. First test group received 1mg/egg aromatase inhibitor (AI), second test group received 1mg/egg Tamoxifen, third test group received 1mg/egg Clomiphene and forth test group received 1mg/egg GAR79 respectively. Chickens were determined after hatching on first day using Feather Sexing method. Redetermination was performed after 45 days for more insurance. In this study 14-α-hydroxy 3,6,17, androstantrion inhibitor with dose of 1 mg/egg were injected.

Results: Administration of anti-aromatases into the eggs during incubation period causes production of male fetus about %72 to %84 that in comparison with control group (%52/5 male) showed an increase of %20 to %34 (P ≥0.05). The sex reversed females have bilateral testes with ability of complete spermatogenesis and also the physical appearance and behavior of normal males.

Conclusion: Results showed the significant role of aromatase in sex differentiation. Moreover, results showed GAR79 as an anti-aromatase could affect aromatase activity in sex differentiation.