Serum soluble interleukin-2 receptor (sIL-2R) levels and T lymphocyte subpopulations were measured in 87 cases of normal pregnancy and 109 normal non-pregnant women as control group. It was found that sIL-2R level and CD8 T subpopulation increased as compared with control group (214,600 +/- 70,400 U/L vs 162,100 +/- 84,100 U/L, P < 0.01; 37.6% +/- 5.3% vs 31.3% +/- 7.0%, P < 0.01), but the ratio of CD4/CD8 was lower than that of control group (1.2 +/- 0.2 vs 1.5 +/- 0.5, P < 0.01). No significant difference was found between CD3, CD4 subpopulations of pregnancy and that of control group (64.1% +/- 7.3% vs 66.0% +/- 9.9%, P > 0.05; 44.1% +/- 5.8% vs 43.8% +/- 9.0%, P > 0.05). And no significant relation was found between sIL-2R level and CD3, CD4, CD8 subpopulations, CD4/CD8 (r = 0.203 2, 0.207 7, 0.103 7, 0.121 4 respectly, P > 0.05). These results suggested that the changes of T lymphocytes and sIL-2R may play an important role in maintaining normal pregnancy and sIL-2R may be one of factors improving fetal survival.