Background. The purpose of the research was to investigate and to evaluate the features of reactivity of the pituitary-adrenocortical system in delivery under chronic pyelonephritis and preeclampsia on the background of the chronic pyelonephritis. Materials and methods. Hormonal investigations were carried out in 140 maternity patients with chronic pyelonephritis and preeclampsia on the background of the chronic pyelonephritis. Results of reactivity of the pituitary-adrenocortical system correspond to the conception of stress and adaptation. Results. Maximal increase of secretion of the pituitary-adrenocortical system by a type «adaptive reactions-sharp stress» was detected in a group of healthy parturients and women with chronic pyelonephritis. The decrease of hormonal activity in parturients with moderate to severe preeclampsia on the background of chronic pyelonephritis depends on the pathological process severity — the levels of the hormonal secretion characterize adaptive possibilities by a type «stress-resistance» and by a pathological type of adaptation — «stress-exhaustion». Сonclusions. The efficiency of proposed therapy has allowed to achieve the physiological reactivity of the pituitary-adrenocortical system in parturients with moderate preeclampsia on the background of chronic pyelonephritis. In parturients with concomitant severe preeclampsia, the adaptive possibilities and hormonal reactivity are increased up to «stress-exhaustion» — «stress-resistance» that enable to optimize the course of labor, intranatal state and postnatal adaptation of newborn.