Anesthesized dogs were exposed to a 30 minute tilt test at 30 degrees. Most significant changes were seen in venous and lymphatic vessels. During the first minutes of the tilt test lymph flow from the thoracic compartment diminished rapidly and later it partially recovered. Pressure in the thoracic lymphatic duct diminished in parallel with that in the jugular vein. Lymph flow from the neck vessel at first increased and then decreased. After the animals were returned to the recumbent position, their venous and lymphatic pressure reached the pretest level. Lymph flow from the thoracic duct increased drastically and then returned to the baseline level. During moderate orthostatic effects lymph circulation undergoes significant changes produced by gravitational shifts and morphofunctional specificities of lymphatic vessels.