The investigation has shown that the antipyrine concentrations in the external pudic artery and the jugular vein were identical after intramammary administration. In the standing unanesthetized goat the antipyrine concentrations in the jugular vein and the external pudic vein were identical, while the concentration in the subcutaneous abdominal vein was always higher. The blood from the mammary gland under these circumstances thus seems to flow exclusively through the subcutaneous abdominal vein, therefore the concentration difference between blood from the afferent and from the efferent mammary vessels can be determined from samples taken from the jugular and subcutaneous abdominal veins respectively. As the concomitantly absorbed amount of antipyrine can also be calculated, it is possible to compute the blood flow through the mammary gland. By use of this method it was shown that the blood flow of the udder of lactating goats varies between 20–90 ml/min. per 100 g mammary tissue and in dry goats from 16–46 ml/min. per 100 g tissue.