This paper disproves Darlington\´s conjecture that every

-grounded two-port is equivalent to a series-parallel two-port. The proof depends upon the construction of a counterexample. This counterexample is a six-node

-grounded two-port, whose admittance functions

written without common factors, have compact poles at the zeros of

and for which

has a negative coefficient. In accordance with properties of

series-parallel networks derived in an earlier paper, the network of the counterexample cannot be equivalent to any

series-parallel two-port.