Sex chromatin (SC) is defined as inactive X chromosome in the female somatic cells, it condensed as heterochromatic at interphase of the nucleus and appears like nuclear satellite projection, and only female cells contain SC in mammals. Different ages of cocks: immature (8,16 weeks old), growing (24 weeks old) and production age (32,48 weeks old) , were studied to detect the sex chromatin (SC) with it's various shapes :Sessile nodule(SS), Drum stick(DS), Tear drop(TD) and Club shape(CS) in the blood lymphocytes of blood smears prepared from WBCs of 45 New Hampshire(NH) strain cocks. Also SC measurements were detected which include: vertical (V) and horizontal (H) axes, SC area (SCA), nuclear area (NA), and the ratio(R) between these two areas. . Results show that SC is present in the male chicken blood lymphocytes in all ages. There is no significant difference in the incidence of the SC or its various measurements between ages, but the vertical axis was recorded a significant (P<0.05) decrease at 16 week old as compared with other ages. Also there is a non significant increase in the incidence of DS shape with ages; this indicated that simple, easy and cheap test could be helpful to detect some physiological parameters in the poultry species and other mammals.