Abstract: Serum IgG, C3, T-lymphocyte subgroups and SBP, DBP were determined in 20 patients before and after treatment with lnter1eukin 2. Among them, 10 cases were ill with advanced carcinoma and essential hypertension （EH）,and the other 10 had advanced carcinoma with non-EH. The results showed that : （1）Small dose administration of IL2 lowered the blood pressure to normal level in EH and the hypotensive effects of IL2 cou1d persist for at least 1 month with no toxic or untoward effects. BP in non-EH was not affected by IL2.（2）Serum IgG in EH was much higher than that in non-EH group （P＜0. 05）. Serum C3 and CD8 in EH were much lower than those in non-EH group （P＜ 0. 05 ）. （3）Linear positive correlation was found between BP and Serum IgG （r= 0. 78） in EH, while linear negative correlation was found between BP and CD, （r = - 0. 67 ）. These results suggest that the hypotensive effects of IL2 are brought about by adjusting immunological system function in EH.