Abstract: The aim of this study was to determine the content of selected heavy metals in birch sap, and to examine whether the tree diameter, the obtained daily sap volume and the date of collection have an impact on their content. Moreover, it was decided to check whether the tree diameter could affect the intensity of the sap leak. The study was carried out in central−eastern Poland, in the Garwolin Forest District, in a stand with a dominant share of silver birch at the age of 65, which grows on a moist mixed broadleaved forest habitat type. Sap from the selected trees was taken after 24 hours of leakage, four times at weekly intervals. In each case, the daily sap volume was measured and the content of lead, nickel, chromium and cadmium was determined. No effect of tree diameter on the content of the studied elements was found. We also proved that the tree thickness had an impact on the daily sap volume. However, a negative relationship was stated between lead and cadmium content and daily sap volume. In turn, over time, birch sap was characterized by increasing concentration of lead and cadmium, while in the case of nickel downward trend was shown for two diameter classes. The obtained results of the determination of the content of heavy metals in birch sap testify to the fact that for most of samples it is characterized by health safety. However, few exceedances of the most restrictive potable water as well as fruit juices and nectars standards are encountered, confirming the susceptibility of birch sap to heavy metal pollution. Therefore, in order to guarantee the safety of consumers, primarily it is necessary to select the collection points taking into account potential industrial and agricultural pollution and secondly – combining birch sap taken from as many trees as possible in order to average a very large variation in the content of heavy metals, both between individual trees and over time. It should also be noted that consuming birch sap taken from only one tree may pose a threat to the health safety of consumer.