In order to induce changes in serum prolactin levels, estradiol benzoate as a hyperprolactinemic agent, and bromocriptine as an antiprolactin drug were used in this stduy. 80 immature male and female rats were divided randomly into five groups for each sex (8 animals for each group). The first group of both male and female rats were considered as control which were daily injected s/c with sesame oil for 10 days. The rest groups were daily injected s/c with estradiol benzoate for 10 days. After 24 hrs. from the last injection, the animals of the 2nd group of both male and female “rats were sacrificed in the morning and the obtained sera stored at -20°C till analysis. The 3rd , 4th and 5th groups were followed by injection of bromocriptine at three dose levels (10, 20 and 40 ug /animal) for 7 days. After 24 hrs From the last injection, the animals of 2nd groups of both male and female Rats were sacrificed in the morning. And the obtained sera stored at -20 C till analysis . The 3rd ,4th and 5th groups were followed by injection of bromocriptine at three dose level (10 ,20 and 40 ug /animal ) for 7 days . after 24 hrs. from the last injection , the animals were slaughtered and the obtained sera were kept at -20 till analysis .the changes in serum interleukin -2 level were determined using ELISA technique and levels of prolactin were measured using RIA Kit. The serum levels of both interleukin -2 and prolactin revealed a significant increase of (308% and 62%)and (146% and 89%) Respectively in male and female immature rats injected with estradiol benzoate (2nd group). In animal groups which were followed by injection of bromocriptine at doses of (10, 20 and 40 ug / animal), the serum level of interleukin-2 and prolactin showed a significant decrease of (10% and 15%), (41% and 49%) and (84% and 75%) orderly in male rats, and (21% and 25%). (56% and 63%) and (86% and 89%) respectively in female rats. Furthermore, the results of the present study revealed a high positive correlation coefficient between interleukin--2 and prolactin.