We studied the effect of immunization on the adrenal gland in 5week-old chickens. The birds were divided into 3 groups: 1)control group; 2)birds that got melatonin during 1 week; 3)birds that got seduxen during 1 week. Half the birds in each group was immunized by human erythrocytes. The peak of the immune reaction was detected on the 7th day after the immunization. To study the adrenal gland activity we used such parameters as: the cell nuclear diameter and the width of interrenal tissue. The data we received showed that melatonin activated synthesis and secretion of glucocorticoids, in general by means of synthesis acceleration. Seduxen does the same, in general by means of secretion acceleration. So seduxen showed the activation effect on adrenal like melatonin, but in a different way. Immunization highly activated synthesis and secretion of glucocorticoids, like in melatonin group, but in this case the effect was more vivid. These results showed that the effectiveness of adrenal functioning was highly dependable on immune processes as well as on epiphysis influence. Immunization in combination with melatonin and seduxen reduced influence of these substances on the adrenal. Though adrenal activation took place, but it was not so intensive as it happened under the influence of seduxen or melatonin only and separately, and it was much less intensive as it happened after only immunization.