The application relates to a medical catheter for hypothermic treatment, with a catheter tube (10), which has at least one through-channel (11) and at least two temperature control channels (12, 13), and with at least one heat exchange element (14), in particular an expandable balloon, which is arranged in a distal catheter portion (15) of the catheter tube (10) and is fluidically connected to the temperature control channels (12, 13) in such a way that a temperature control circuit is formed. The application is characterized in that the catheter tube (10) has a smaller external diameter in the distal catheter portion (16) than in a proximal catheter portion (15).
