Glypressin is a vasopressin derivative which is used in the present study to stop pulmonary bleeding. The effects of endobronchially versus intravenously applied glypressin were examined during diagnostic fibreoptic bronchoscopy in 27 patients. Transcutaneously measured blood gases and haemodynamics were analysed after 1 mg glypressin was given. The glypressin plasma level was 251 fold higher after the intravenous than after the endobronchial administration. After endobronchial application no significant changes were observed for blood pressure, heart rate or blood gases. Following the intravenous glypressin application there was a significant increase in diastolic blood pressure. The bronchial mucosa pallor appeared earlier after topical than after systemic glypressin application. The haemostyptic effect was similar for both routes of application.