Plasma concentrations of Epidermal Growth Factor (EGF) in healthy control persons do not change significantly during adult lifetime and no diurnal changes could be detected. In addition, no alterations of plasma EGF concentrations occur during acute and chronic stress and in all three trimesters of pregnancy. Thus, the previously suggested theories that EGF might play a causative role in the activation of the hypothalamic-pituitary adrenal axis during the stress reaction and in the prevention of peptic ulcers in pregnancy could not be confirmed by the present data.