Infusions with stepwise increasing concentrations of epinephrine (from 2.5 to 10 micrograms/min) and norepinephrine (0.5-2.0 micrograms/min) were given to normal subjects. During infusion of epinephrine there was a clear rise of the serum parathyroid hormone (PTH) levels already at the lowest concentration. Concomitantly there was a fall in the serum concentrations of calcium. The PTH levels returned to baseline promptly after termination of infusion whereas hypocalcaemia persisted up to 30 minutes, indicating a primary response of PTH to epinephrine. When propranolol was given prior to and during the epinephrine infusion no significant changes occurred for either PTH or calcium. During infusion of norepinephrine no consistent significant changes were noted for either PTH or serum calcium. Thus, our data do not support any concept of a basal adrenergic tone which normally modulates the secretion of PTH. However, during conditions of stress the beta-adrenergic stimulation night be of importance.