Preeclampsia origin has no conclusive explanation. As part of its etiology it has been proposed immunologic disorders. This work explores several lymphocytes subsets and postulates possible mechanisms involved in a lost of immune tolerance in this entity. To compare cellular populations of CD3+ CD56+, CD4+ CD25+, T lymphocytes (CD4+ and CD8+) and NK cells subsets in preeclamptic and pregnant healthy women. Through flow cytometry antibodies, peripheral blood mononuclear cells were obtained from both groups of patients. CD3+ CD56+, CD4+ CD25+, T lymphocytes (CD4+ and CD8+) and NK cells were identified. Mean and standard deviation, Student ttest and Pearson correlation were calculated to analyze differences between groups and correlation between mean blood pressure and different lymphocytes subsets; p < 0.05 was considered significant. CD3+ CD56+ cells percentage was lower in preeclamptic patients (2.7 vs 6.1%; p < 0.002), CD4+ CD25+ cells percentage tend to be lower too (22.11 vs 33.86; p = NS). Mean blood pressure shown negative correlation with CD3+ CD56+ cells percentage (rp - 0.666; p = 0.001) and with CD25 on CD4+ T lymphocytes surface (rp - 0.526; p < 0.025). Based on the association between mean blood pressure and lymphocytes percentage for these two cellular subsets, data obtained suggest that CD3+ CD56+ and CD4+ CD25+ cells play an important role in preeclampsia development.