Serum IgG levels were significantly increased (P less than 0.001) in 33 (20 male and 13 female) essential hypertensive cases (mean = 2083.87 +/- 99.94 mg/dl) when compared to 30 (15 male and 15 female) random normotensive control subjects (mean = 993.84 +/- 72.25 mg/dl). Of the 33 cases, 12 (36.3%) were familial and the rest were sporadic. No significant difference was observed in the IgG levels between familial and sporadic cases. Similarly, no significant difference was found between male and female hypertensive patients both in the familial and the sporadic group or between smokers and non-smokers. However, the levels of IgG were found to be increased in the initial stages of onset of the condition (duration of less than 1 yr). The present study supports the probable involvement of immunological responses in essential hypertension.