The role of atrial natriuretic factor (ANF) in the genesis of primary hypertension is not clear. However, a natriuretic and blood pressure lowering effect has been observed after infusion of ANF. Therefore, subjects at risk of future hypertension might be deficient in ANF or less responsive to it. To address this question we studied ANF, sodium excretion and blood pressure in 180 young normotensive people with different probabilities of developing hypertension later in life. The 180 subjects had either two, one or no hypertensive parents. Sixty-nine offspring had a high, 58 an intermediate and 53 a small probability of developing hypertension ('high', 'mixed' and 'low' groups). Mean plasma levels of ANF did not differ among the three groups of offspring. A negative association was found between ANF and diastolic blood pressure, being most pronounced in the low-risk group. The similar levels of plasma ANF in these groups suggest that ANF is not directly related to the development of high blood pressure.