The work was conducted to clarify the development of testes and histological changes of the Seminiferous tubules that is the Surface area, diameter, length of the tubules and the process of Spermatic cells growth in Seminal epithelium in relation to Sexual maturity of the meat-type cockerels. In addition the present experiments were planned to gain some basic data helpful for the study of reproductive physiology in meat-type cockerels and also to compare the histological changes Seminiferous tubules between egg and general purpose type cockerels. 1. The growth pattern of body weight, testes and comb was classified into four phase according to age. Body weight increased up to about 2kg at 2nd stage and to 4.3kg at 4th stage while at 3rd stage the growth rate of body weight was slower. The tests developed slowly until 22 weeks of age with no correlation to the growth of body weight. However, it grew rapidly afterwards, reaching 27.79$pm$9.26gm and 42.46$pm$5.33 gm at 24 and 28 weeks of age, respectively. The spermatozoa was seen first at 24 weeks of age. On the other hand, comb grew at similar rate to the testes, weighing on the average 21.78$pm$6.48gm and 41.42$pm$1.25gm at 24 and 28 weeks of age, respectively. 2. The areal rate of the Seminiferous tubules to interstitial tissues was 66%:34% at 2 weeks of age and the rate of the former increased in comparison to that of the latter as they grew older, becoming 94%:7% between at 24 weeks of age, when the testes weight increased rapidly too. 3. Diameter of Seminiferous tubules at 2 weeks of age was 42.76$pm$1.04$mu$m and then it gradually increased as the testes grew until 22 weeks of age, when it grew rapidly, increasing about 2.9 times of those of 2 weeks and at last increased up to 5 times at 24 weeks. 4. Length of Seminiferous tubules was 4.5cm at 2 weeks and then it was gradually increased. At 22 weeks old the length of tubules was icnreased rapidly being 321 meter and increased more than double, being 658 meter at 24 weeks old. 5. The cells of Seminal epithelium developed poorly and the number of cells were relatively few until 16 weeks old. Afterwards the cells increased rapidly in number and at 18 weeks, the number became twice of those of 16 weeks, reaching 140.43$pm$43.6. At 24 weeks the cells increased more rapidly, reaching to 10 layers and Spermatozoa were first time seen.