Abstract: A microdialysis probe comprises a tubiform probe body, a tubiform dialysis membrane disposed distally of the probe body, and flexible conduits for adducing and abducing dialysis fluid, distal end portions of which are disposed in the probe body. Apart from the conduit portions disposed externally of the probe body the probe is substantially rotationally symmetrical. One of the conduits, preferably the abducing conduit, comprises an S-shaped portion inside of the probe, adjacent to the distal end of the other conduit. Also disclosed is an assembly of the probe and a cannula for inserting it into tissue; after insertion the cannula can be withdrawn in a proximal direction.