Uremia induces a suppression of the immune status. A large clinical literature suggests that estradiol (E-2) plays a critical role in immune function. A large proportion of women hemodialysis patients faced early menopause and inadequate estrogen levels. The aim of the present study is to evaluate the effect of hormone replacement therapy on immune function in terms of CD4(+) numbers (inducer/helper T cells), CD8(+) numbers (cytotoxic/ suppressor T cells), CD4(+)/CD8(+) ratio, and IgG, IgM, IgA levels in woman hemodialysis patients. In our study, 15 female hemodialysis patients (median age 32.6 range 24-45) were treated with triphasic estrogen/progesterone preparation (estradiol 2 mg for 10 days, and afterwards estradiol 2 mg+norethisterone 1 mg for another 10 days, and at the end estradiol 1 mg for 6 days) for 6 months. CD4(+) numbers, CD8(+) numbers, and IgG, IgA, and IgM levels were determined before and after HRT. The "paired-samples T" test was used for statistical analysis of pretreatment and posttreatment values. A significant increase was observed for CD4(+) numbers (582 +/- 435 versus 637 +/- 445, p=0.04) and CD4(+)/CD8(+) ratio (1.4 +/- 0.16 to 2.4 +/- 0.3, p<0.01) after hormone replacement therapy (HRT). Serum immunoglobulin levels were not changed significantly. In conclusion, in postmenopausal hemodialysis patients, HRT significantly increased CD4(+) numbers and CD4(+)/CD8(+) ratio, but no effect was observed in IgM, IgG, and IgA levels. Long-term clinical effects of HRT on immune system should be investigated in dialysis patients with further studies.