  A proof for a non-perturbative C-theorem in four dimensions, capturing the
irreversibility of the renormalization group flow in the space of unitary
quantum field theories, has not been accomplished, yet. We test the conjectured
C-theorems using the exact results recently obtained in N=1 supersymmetric
gauge theories. We find that the flow towards the infrared region is consistent
with the main proposals for a C-theorem.
