We determined plasma aldosterone levels of patients with healthy adrenals after rest (n = 80) and exercise (n = 30) using a radioimmune assay with highly specific antibodies. The obtained normal values had a log-normal distribution. The normal values did not show any differences regarding sex and age. At rest they ranged between 50 pg/ml and 190 pg/ml, after exercise between 110 pg/ml and 310 pg/ml.