Several studies in human and experimental models indicate the existence of a partial relationship between essential hypertension (EH) and the immune system. In this study, cellular immune functions were investigated in 13 patients with untreated and uncomplicated essential hypertension (EHP) and in 10 of their offspring (EHO) and compared to 13 age- and sex-matched normotensive controls (NC) and 10 of their offspring (NCO). The total number of T cells and T cell subsets were similar in all groups examined. In the EHP, basal lymphocyte transformation without lectins was significantly lower (1,126 ± 261 cpm of [<sup>3</sup>H]-thymidine uptake) than in the NC (3,223 ± 736, p < 0.01); the response to both phytohemagglutinin (PHA) and concanavalin A (ConA) revealed reduced [<sup>3</sup>H]-thymidine uptake as compared with NC (21,890 ± 5,432 compared to 64,574 ± 9,723 for PHA and 10,488 ± 2,621 compared to 37,334 ± 8,148 for ConA, respectively, p < 0.01). However, the ability to proliferate as a response to lectins was normal. This was leading to a normal stimulation index in both groups. In the EHO, non-significant decrease in basal transformation and reduced uptake with PHA (49,537 ± 7,478) versus NCO (69,911 ± 7,254) and NC (64,574 ± 9,723) were found. These findings suggest that the proliferative response of T lymphocytes is partially suppressed in EH.